If Jessica drives her car for 2.5 hours at a constant speed,

If it were not mentioned that the speed is constant, then the second statement wouldn't make sense: what speed it would refer then?

If Jessica drives her car for 2.5 hours at a constant speed, did the total distance she traveled exceed 175 miles?

d=r*t

(1) Jessica drove her car a distance of 100 miles in the first 75 minutes.
If Jessica drove 100 miles in 75 minutes she is traveling 1.25 miles/minute. If she travels at a constant speed (as is stated in the stem) then she travels 1.25 miles/minute for 2.5 hours (150 minutes)
d=r*t
r=1.25
t=150
d=1.25*150
d=187.5
SUFFICIENT

(2) At the same speed, Jessica would cover a distance of 320 miles in 4 hours.
If she travels at a constant speed and covers 320 miles in 4 hours then she drives 80 miles/hour or 1.33 miles/minute. As we saw in statement 1, a constant speed of 1.25 miles/minute is more than enough to cover 175 miles in 2.5 hours. Therefore, a greater constant speed will ensure she travels more than 175 miles in 2.5 hours.
SUFFICIENT

(D)

Each statement alone is enough to answer this questions