Which of the following sentences are correct ?
a Long sightedness is corrected by convex lens.
b. Short sightedness is corrected by convex lens.
c. Long sightedness is corrected by concave lens.
d, Short sightedness is corrected by concave lens.
1
Only a and b are correct
2
Only b and c are correct
3
Only cand d are correct
4
Only a and d are correct