Concept:
Use the inclusion-exclusion principle:
$$n(M \cup E)=n(M)+n(E)-n(M \cap E)$$
where $M$ = Malayalam speakers and $E$ = English speakers.
Step 1: Substitute given values.
Total persons = 100
Malayalam speakers:
$$n(M)=80$$
English speakers:
$$n(E)=60$$
Assuming everyone speaks at least one language:
$$n(M \cup E)=100$$
Step 2: Find common speakers.
Using formula:
$$100=80+60-n(M \cap E)$$
Step 3: Solve for intersection.
$$100=140-n(M \cap E)$$
$$n(M \cap E)=40$$
Step 4: Find English only speakers.
English only means:
$$n(E)-n(M \cap E)$$
So:
$$60-40=20$$
Step 5: Select the answer.
Therefore, the number of people who speak English only is:
$$20$$
Hence the correct answer is (C) 20.