Which one of the following statements is correct regarding aqueducts ? 1. The choice of a particular type of aqueduct does not depend upon its length. 2. The selection of a type of aqueduct lies on the considerations of economy. 3. On a very wide drainage, Type III aqueduct is most economical. 4. In Type III aqueduct, the width of the aqueduct is minimum but the cost of bank connections is maximum. Select the correct answer using the code given below :
- A2 and 4
- B1 and 3
- C1 and 2
- D3 and 4Correct
Solution
Concept
Types I, II and III of aqueducts
Step-by-step solution
1. The type depends on the length (width of the drainage), so statement 1 is false. 2. In Type III (rectangular masonry trough) the width is the least, but the bank connections are the longest and costliest (statement 4 correct). 3. For a very wide drainage, the saving from a narrow trough outweighs the high cost of bank connections, so Type III is most economical (statement 3 correct).
Explanation
Type I aqueducts carry the canal on an earthen bank across the drainage (widest, small bank connections) and suit narrow drainages. Type III has a narrow rectangular trough and long bank connections, and suits very wide drainages.
Why the other options are wrong
Statement 1 is wrong because the length decides the type, which removes options (b) and (c). Option (a) pairs statement 4 with 2 but leaves out statement 3, which is a correct statement of the economic choice.
Shortcut
Narrow drainage → Type I; very wide drainage → Type III.
Common mistake
Thinking that the length does not matter.
Correct answer: D) 3 and 4