(Taking up) more space than (any other) planet (in our galaxy), Jupiter is larger (than the size of) Mercury, Venus, Earth, and Mars combined. (No Error)
Answer is D - (than the size of). Why though?
You’re comparing a planet and size. You need to compare planets to planets (Jupiter is bigger than Mars) or size to size (the size of Jupiter is bigger than that of Mars).
(Actually, you must do the former because saying a “size” is “bigger” is redundant–“bigger” already includes the idea of “size”)
@marvin100 Thank you so much!