Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A): T.W. Engelmann's experiments with Cladophora and aerobic bacteria led to the development of the first action spectrum of photosynthesis.
Reason (R): Engelmann observed first that aerobic bacteria accumulated primarily in areas of blue and red light, which correspond to the absorption spectra of chlorophyll a and b.
In light of the above statements, choose the correct answer from the options given below.