In 1517, the Italian physician Girolamo Fracastoro was probably the first person ---- that fossils are animal remains; however, it was not until the 18th century that scientists ---- to realise that fossils can tell us a great deal about the history of living things.
A) suggesting /had begun
B) being suggested /were beginning
C) to have suggested /have begun
D) to suggest /began
E) having suggested /were going to begin