[A]: Xanthium will not flower if the long dark period is interrupted by a single brief flash of light.
[R]: Xanthium is a long day plant where con- tinuous long loght period as essential for flowering.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

C