The slenderness ratio for masonry walls should not be more than A. 10 B. 20 C. 30 D. 40

The correct answer is A. 10.

The slenderness ratio is a measure of the stability of a slender column or wall. It is defined as the ratio of the unsupported length of the column or wall to the least radius of gyration of its cross-section.

The slenderness ratio of a masonry wall should not be more than 10, as this is the maximum slenderness ratio that can be safely supported by a masonry wall. If the slenderness ratio is greater than 10, the wall will be more likely to buckle under load.

The other options are incorrect because they are greater than the maximum slenderness ratio of 10.