Which one of the following is not a digestive enzyme?

The major chemical compound found in human kidney stones is

A. Urea

B. Calcium carbonate

C. Calcium oxalate

D. Calcium sulphate

The carbon dioxide content in the air that we exhale is about

A. 4%

B. 8%

C. 12%

D. 16%

In which of the following creatures haemoglobin is dissolved in protoplasm?

A. Frog

B. Fish

C. Human

D. Earthworm

Consider the following.
Assertion (A): Alum is applied to stop bleeding from cuts.
Reason (R): Blood is a colloidal system containing colloidal particles. The aluminium ions of alum have high coagulating power so the blood gets coagulated.
Select the correct answer:

A. Both (A) and (R) are true and (R) is the correct explanation of (A)

B. Both (A) and (R) are true, but (R) is not the correct explanation of (A)

C. (A) is true, but (R) is false

D. (A) is false, but (R) is true