Which of the following statements is true?

fossilization can only occur when oxygen is present.
soft body parts are well preserved as fossils.
a cast fossil leaves a hollow space once occupied by a dead organism.
vertebrate fossils are more common than invertebrate fossils.

The statement in the option #4 is true; Vertebrate fossils are more common than invertebrate fossils. The majority of the fossils are vertebrate skeleton or bones than the invertebrate ones. The options 1,  2, 3, is rather wrong, that leaves you with option #4. 

a. both scientists had different interests.

Explanation:

Newton focused in physics for the most part and the study of what we know now as Newton's laws

while Gallileo focused on planets and astrology