Which one of the following completes the given statement correctly ?
Cretinism is a human disorder which is due to the under secretion of

Ordinary table salt is sodium chloride. What is baking soda?

A. Potassium chloride

B. Potassium carbonate

C. Potassium hydroxide

D. Sodium bicarbonate

Ozone hole refers to

A. hole in ozone layer

B. decrease in the ozone layer in troposphere

C. decrease in thickness of ozone layer in stratosphere

D. increase in the thickness of ozone layer in troposphere

Pine, fir, spruce, cedar, larch and cypress are the famous timber-yielding plants of which several also occur widely in the hilly regions of India. All these belong to

A. angiosperms

B. gymnosperms

C. monocotyledons

D. dicotyledons

Pollination is best defined as

A. transfer of pollen from anther to stigma

B. germination of pollen grains

C. growth of pollen tube in ovule

D. visiting flowers by insects