What is the main commercial source of helium?

What is the main commerical source of helium ?

Name the main commercial source of helium.

What is the commercial sources of helium?

(A) Helium is present in radio active minerals like pitchblende, monazite and clevite (R) The main commercial source of helium is natural gas

Main source of helium is

What is the commercial source of cork? How is it formed in the plant?

What is the commercial source of cork? How is it formed in the plant?

What is the commercial sources of cork. How is it formed in plant?

What is the main source of heavy water?