During digestion, hydrochloric acid (HCl) lowers the stomach's pH and this causes the enzyme pepsinogen to be converted to its active form, called pepsin. Pepsin is a proteolytic enzyme, which means it cleaves (breaks) peptide bonds assocciated with food particles. The enzyme pepsin can also cleave pepsinogen into pepsin, and this causes the rate at which pepsinogen is converted to pepsin to increase. This is an example of:

Catalysis

Explanation:

Pepsin is able to break peptide bonds, turning large protein molecules into small peptide chains.

When pepsin acts to break down pepsinogen (inactive form of pepsin), it is accelerating pepsinogen → pepsin reactions, acting as a catalyst, reducing activation energy and favoring proteolytic reactions at a higher rate.

This process of accelerating reactions is characteristic of enzymes and is known as catalysis.

explanation:

i think option no d is the correct answer

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2