Ephedrine is obtained from the plant part of Ephedra known as
Ephedrine is the sympathomimetic amine and it is commonly used as a stimulant. The herb Ephedra sinica is used in traditional Chinese medicine, contains ephedrine and pseudoephedrine. The stems are the source of famous drug ephedrine and stem contain the other alkaloid, pseudoephedrine.
So, the correct answer is 'Stem'.
The correct choice is C.