In Belgium method of tunnelling_____.

A. Construction of side walls is completed before invert and roof arch are built
B. Construction of roof arch is completed before side walls and inverts are built
C. Construction of invert is completed before side walls and roof arch are built
D. Construction of invert and side walls is completed before roof arch is built

Answer: Option B.

Explanation:

IS 14665 gives details about elevators. It specifies the number, capacityof elevator and number of floors to be served.