D.

controls multiple traits in an individual

Pleiotropic gene is a gene that controls multiple traits is an individual. It is also called polyphenic gene, e.g., phenylketonuria causing multiple adverse effects due to the mutation in a single gene coding for enzyme phenylalanine hydroxylase.

D.

Application of iron and magnesium to promote synthesis of chlorophyll

If a pulse crop possesses premature yellowing of leaves and decrease in yield and application of magnesium and iron to promote synthesis of chlorophyll may become most beneficial to overcome the problem and to obtain maximum seed yield.
Magnesium is an important part of ring structure of chlorophyll molecule and its deficiency causes chlorosis and premature leaf abscission.
In iron deficiency also, the leaves become chlorotic because iron is required for the synthesis of some of the chlorophyll protein complexes in the chloroplast.

D.

Vitamin A

Golden rice is a variety of rice produced through genetic engineering to biosynthesize -carotene, a precursor of vitamin-A, in the edible parts of rice. 

A.

1960's

Green revolution is the rapid increase in agricultural production (especially wheat and rice) during 1960-70. It has been achieved through introduction of high yielding varieties, increased irrigation facilities, fertilizer application, pesticides and agriculture management, Dr. MS Swaminathan is known as Fathe of Green Revolution in India.

A.

alkaline pH of the insect gut

The Bt toxin is an inactive protoxin, which is activated due to the alkaline pH in the insect gut. 
Bt toxin dissolve in high pH of insect gut and become active. The toxins then attack the gut cells of the insect, punching holes in the lining. 
(i) Insect eats Bt crystals and spores. 
(ii) The toxin binds to specific receptors in the gut and the insects stops eating. 
(iii) The crystals cause the gut wall to break down allowing spores and normal gut bacteria to enter the body. 
(iv) The insect dies as spores and gut bacteria proliferate in the body.