Which of these statements must be true if two different plants are members of the same species?
a) they have the same number of chromosomes as one another.
b) they both produce flowers and seeds at the same time of year. c) their leaf shapes and patterns appear to be exactly the same.
d) they can produce offspring plants that also produce fertile seed.

As it is given in the question that both the plant belongs to same species and according to biological species concept, a species can be defined as the largest group of organisms in which any two two individuals of the opposite sex breed to produce a fertile offspring.

According to this the correct answer is D) They can produce offspring plants that also produce fertile seed.  

D

Explanation:

They can produce offspring plants that also produce fertile seed.

the answer is c.) there is a warm front in region a and a stationary front in region b.