മനുഷ്യ ശരീരത്തില്‍ ഏറ്റവും കൂടുതല്‍ ഉള്ള മൂലകം:

Demography is the study of:

Light year is the unit of:

Theory of relativity is associated with:

The instrument to test the purity of milk?

The study of relation of animals and plants to their environment?