When she began studies in the 1920s, scientists had only recently began to consider genetics a field of study and accept the research of Gregor Mendel (1822-1884).
A. No change
B. had only recently begun
C. have only recently began
D. have only recently begun
The answer is B, I don’t understand why it is though… When do you know to use had/have? Scientists is plural, so shouldn’t you use have? I thought the answer was D…