Medical science has not done anything yet to solve the problem of the common cold because:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. viruses are so much smaller than the bacteria that cause many other infections; they cannot be seen with ordinary microscopes.
It is clearly mentioned in the passage:
“...because they are so much smaller than the bacteria which cause many other infections, viruses cannot be seen with ordinary microscopes. Nor can they be cultivated easily in the bacteriologist’s laboratory...”
This directly explains why medical science has not yet been successful in solving the problem of the common cold.
Hence, the chosen option will be correct.