Concept:
Different ploughs are used according to soil condition, depth of ploughing, and field operation requirement.
Step 1: A disc plough cuts and turns soil using concave discs.
Step 2: A disc harrow breaks clods and pulverizes soil using gangs of discs.
Step 3: A harrow plough combines the working principles of a regular disc plough and a disc harrow.
Step 4: It is suitable for shallow ploughing and light soil working.
Step 5: Therefore, the correct answer is harrow plough.
\[
\boxed{\text{Harrow plough}}
\]