Q: Just as the outer surface of a spacecraft expands and shrinks as it is exposed to and shielded from the sun,
so the outer crust of the Earth expands and contracts each solar day, although changes in the Earth's crust are more difficult to detect.
A.
so the outer crust of the Earth expands and contracts each solar day B. the outer crust of the Earth has been expanding and contracting each solar day
C. there has been, each solar day, an expansion and contraction in the outer crust of the Earth
D. so the Earth's outer crust expands and, each solar day, contracts
E. similarly, the outer crust of the Earth expands and contracts each solar day
Solution: The idiom is ‘Just as the …… so the …..’So we can eliminate B, C, E
D – changes meaning- sounds like ‘contracts’ is modifying ‘each solar day’ and not ‘outer crust’
This leaves us with
A – which is idiomatic