Explanation:

Alright, let’s break it down step by step:

- The question is: What is the speed of the train?

- Statement I: The train takes 40 seconds to pass a bridge 1200 m long.

- Statement II: The train takes 8 seconds to pass a telegraph pole.

What do these two tell us?

- Alone, each tells you part of the story:

- Statement I: Combined with the unknown length of the train, you can’t directly get the speed just from this. You don’t know the train’s own length.

- Statement II: Passing a pole gives you the train’s length—because the train completely clears the pole in that time. But alone, it’s not enough for speed unless you know how much ground is covered over a certain time.

- Together: Here’s the important bit—combine them.

- From II: You get the train’s length (speed × 8 seconds).

- Use this length plus the bridge length (from I), and the time taken (40 seconds). Now you’ve got two equations, two unknowns—you can solve.

- Only with both together can you answer the question.

Options recap:

- Option 1: Either one, but not both, is enough. Nope.

- Option 2: Either one alone is enough. Again, no.

- Option 3: Both together, not alone, are needed. ? This is the correct answer.

- Option 4: Even together, not enough. That’s not right.

CORRECT ANSWER: Option 3