The correct answer is A. 1 in 40.
A verandah (corridor) floor should have an outward slope of 1 in 40. This means that for every 40 feet of length, the floor should slope downward by 1 foot. This slope is necessary to prevent water from pooling on the floor and causing damage.
Option B, 1 in 50, is not a common slope for verandah (corridor) floors. It is possible that some verandah (corridor) floors have a slope of 1 in 50, but it is not the standard.
Option C, 1 in 60, is also not a common slope for verandah (corridor) floors. It is possible that some verandah (corridor) floors have a slope of 1 in 60, but it is not the standard.
Option D, 1 in 70, is not a common slope for verandah (corridor) floors. It is possible that some verandah (corridor) floors have a slope of 1 in 70, but it is not the standard.
The standard slope for verandah (corridor) floors is 1 in 40. This slope is necessary to prevent water from pooling on the floor and causing damage.