Answer: A. IgA

Explanation: IgA is the first line of defense, especially in mucosal areas. It plays a crucial role in immune protection by neutralizing pathogens at the entry points, such as the respiratory and gastrointestinal tracts.

Answer: A. Commercial

Explanation: The .com top-level domain is primarily used for commercial websites. It indicates that the site is intended for business or commercial purposes and is the most widely recognized domain for online commerce.

Answer: B. Schedule H

Explanation: Ibuprofen is classified as a Schedule H drug, meaning it is available only with a prescription. This classification is due to potential side effects and the need for medical supervision during its use.

Answer: D. Palitaxel

Explanation: Palitaxel is considered a Class IV drug due to its low solubility and low permeability. These properties make it challenging to formulate, often requiring advanced drug delivery techniques to achieve therapeutic levels.

Answer: B. ########

Explanation: Gastric lipase is activated in an acidic environment, with an optimal pH range of 4 to 5. This acidity is necessary for the enzyme to catalyze the hydrolysis of dietary fats effectively in the stomach.

Answer: D. Kinetic energy

Explanation: At a given temperature, the average kinetic energy of molecules in all ideal gases is the same, regardless of their mass. This principle is a cornerstone of the kinetic molecular theory of gases.

Answer: B. Poly (vinyl acetate)

Explanation: Polyvinyl alcohol is produced by hydrolyzing poly(vinyl acetate). This chemical transformation converts the acetate groups into hydroxyl groups, yielding a water-soluble polymer used in adhesives, coatings, and various industrial applications.

Answer: A. K

Explanation: Lysine (K) is generally not phosphorylated during enzyme regulation. In contrast, serine, threonine, and tyrosine are common targets for phosphorylation, which modulates enzyme activity and cell signaling.

Answer: C. NMDA antagonist

Explanation: Memantine acts as an NMDA receptor antagonist, blocking excessive glutamate activity that can lead to excitotoxicity. This mechanism is particularly beneficial in conditions like Alzheimer’s disease where neuroprotection is needed.

Answer: B. The molecular configuration is chiral

Explanation: For a compound to exhibit optical activity, it must be chiral, meaning it cannot be superimposed on its mirror image. This asymmetry allows it to rotate plane-polarized light.

Answer: A. acetic anhydride and conc. sulphuric acid

Explanation: The Liebermann-Burchard reaction employs acetic anhydride and concentrated sulphuric acid as reagents to detect sterols, producing a characteristic color change that confirms the presence of sterol compounds.

Answer: C. Afimoxifene

Explanation: Afimoxifene is the compound among the choices that does not contain a heterocyclic ring. Its molecular structure lacks the cyclic heteroatom framework present in the other listed compounds.

Answer: B. Sodium lauryl sulfate

Explanation: Sodium lauryl sulfate is a well-known anionic surfactant used extensively in cleaning agents and personal care products because it effectively lowers surface tension and aids in emulsification.

Answer: B. 10 carbons

Explanation: Menthol is a monoterpenoid that contains 10 carbon atoms. Its structure is responsible for the characteristic cooling sensation and minty aroma used in various medicinal and cosmetic products.

Answer: B. Vitamin D

Explanation: Rickets is primarily caused by a deficiency of Vitamin D, which is essential for proper calcium absorption and bone mineralization. Insufficient Vitamin D leads to soft, weak bones in children.

Answer: C. Slowness of performed movement

Explanation: Bradikinesia refers to the slowness in executing voluntary movements. It is a common symptom observed in neurological disorders such as Parkinson’s disease, affecting overall motor performance.

Answer: A. Cascade impactor

Explanation: A cascade impactor is used to determine the particle size distribution of aerosols by separating particles based on their aerodynamic diameters. This method is essential in pharmaceutical and environmental testing.

Answer: D. Area of each signal

Explanation: In NMR spectroscopy, the integrals represent the area under each resonance peak, which is proportional to the number of nuclei contributing to that signal, thereby providing quantitative structural information.

Answer: B. Streptomycin

Explanation: Streptomycin is contraindicated in pregnant women because it can cause ototoxicity and fetal harm. It is therefore avoided in favor of safer antitubercular agents during pregnancy.

Answer: C. 1 ppb

Explanation: Cryogenic shims improve magnetic field homogeneity in NMR spectroscopy to as good as 1 part per billion. This enhancement greatly increases spectral resolution and the accuracy of molecular structure determination.