This is a suggested solution to the question in GCE O Level Pure Physics Paper 1, MCQ question 7.
The answer is A. That is, 800N.
Resultant Force, F = Driving Force – Frictional Force = ma
Given : a = 2.5 m/s2
Therefore, F= 800kg x 2.5 m/s2
Driving Force = Resultant Force – Frictional Force
= 2000 – 1200 = 800N