Chemiosmosis is the diffusion of ions across a selectively permeable membrane. More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration.

ATP synthase is the enzyme that makes ATP by chemiosmosis. The generation of ATP by chemiosmosis occurs in chloroplasts and mitochondria as well as in some bacteria.

Hence, the correct option is (A).

As given, the temperature is increased from T₁ to T₂, then new constants become k₃ and k₄ respectively. 

Rate constant increases with increase in temperature. 

So, k₁ < k₃ and k₂ < k₄.

Hence, the correct option is (B).

The movement of water and minerals in xylem and the movement of phloem sap in phloem is unidirectional and bidirectional respectively. Plants need water for their growth, and it uptakes water through the roots. Water that is taken by the roots has to reach all the leaves or branches, here the xylem function as transportation of water. Therefore, the movement of water and minerals in xylem is always an unidirectional. Whereas, the movement of phloem is bidirectional this is because, once the food is synthesized it is the phloem that transfers the food to all the parts of plants wherever it is necessary.

Hence, the correct option is (A).

Sexually transmitted diseases or infections caused by bacteria can be treated while viral infections can just be managed and not cured. A single dose of antibiotic can cure STDs like gonorrhoea, syphilis, chlamydia. However, diseases such as Genital Herpes or HIV can be managed only with anti-viral drugs. These drugs cannot cure the infection but only limit the length and severity of outbreaks. Further, it can reduce the likelihood of transmission of the disease.

Hence, the correct option is (A).

Nucleophiles are the species which have an excess of electrons.

Among the given species, the lone pair of nitrogen of pyrrole (B) is involved in the delocalization of the ring, thus, they are not available for donation. 

In aniline (D), the lone pair is involved in conjugation with the π electrons of the ring while in pyridine, these are relatively free for donation. Thus, the nitrogen of pyridine (A) is the most nucleophilic.

Phenyl and −COCH₃ ​both are electron-withdrawing groups, thus decreases the nucleophilicity of nitrogen.

Hence, the correct option is (A).

All Cnidarians have tentacles with stinging cells in their tips which are used to capture and subdue prey. In fact, the phylum name "Cnidarian" literally means "stinging creature." The stinging cells are called cnidocytes and contain a structure called a nematocyst. The nematocyst is a coiled thread-like stinger. Stinging justifies their anchorage and defense.

Hence, the correct option is (D).