1, originally 7/30. Let the simplest score be a/b, according to the known, a+2/b=3/ 10, a/b-2= 1/4,

So we get 10(a+2)=3b, 4a=b-2, and we get a=7 and b=30.

Only two people got an a.

So A is not optimal, because if A is optimal, everyone is optimal.

Similarly, if B is excellent, BCD is particularly excellent.

Therefore, only C is the best, and two people can get the best.

C and d got straight as.

3. Find the sum of the weights of three people: (75.5+77.6+73.1) ÷ 2 =113.1kg.

Subtract the sum of their weights: temperature =113.1-75.5 = 37.6kg.

Liangliang =113.1-77.6 = 35.5kg.

Qiang Qiang =113.1-73.1= 40kg.

4. If the whole journey takes 1 as the unit, the time for the express train to meet the local train is1÷ (1/8+112) = 24/5 hours.

Let the whole journey be x kilometers, and x/8 × 24/5-x/ 12 ×24/5=48.

x=240