Re: In his experiments with gravity, Isaac Newton showed how the

Had it been the case that A was: "of all the other planets, each contributing according to its"

Then there is a very little difference between A and D,
Can any one please let me know if the following sentences are correct and is it ok to write in this way:

blah blah ... combined gravitational pull of the Sun and of all the other planets, each contributing according to its ...
blah blah ... combined gravitational pull of the Sun and all the other planets, each contributing according to its ...

We have removed the of part, is it ok to use it just once as in the second sentence?