Question

a car constrained to the speed limit could be tested in only a small subset of real driving situations. source: slate
in this sentence, constrained means:
carried with difficulty
pieced together with a new part
moved to a different location
held back

Explanation:

The car is restricted by the speed - limit, so "constrained" means being held back in this context. The other options do not fit the meaning in the given sentence.

Answer:

D. held back