Select the option that expresses the given sentence in passive voice.…

The correct answer is Option (2) → The old foot overbridge at Itarsi station is going to be replaced by the railway authorities next year.

Passive of “be going to” + verb:

Change	Active	Passive	Why
Object becomes subject	the old foot overbridge at Itarsi station	The old foot overbridge at Itarsi station	The overbridge receives the action, so it becomes the subject.
“Going to” kept	are going to replace	is going to be replaced	“Are going to replace” shows a plan for the future. In the passive it becomes is / are going to be + past participle (V3). “Is” because the overbridge is one.
Agent (by ...)	The railway authorities	by the railway authorities	The railway authorities are named, so the doer comes after “by”.
Full sentence	The railway authorities are going to replace the old foot overbridge at Itarsi station next year.	The old foot overbridge at Itarsi station is going to be replaced by the railway authorities next year.

Other verbs after “going to” work the same way: going to + verb → going to be + V3. Example: Our school is going to hold a blood donation camp. → A blood donation camp is going to be held by our school.

Why the Other Options are Incorrect?

Option 1: The old foot overbridge at Itarsi station is going to replace by the railway authorities next year. — Incorrect. The word “be” is missing. Without it, the overbridge becomes the one that replaces something.

Option 3: The old foot overbridge at Itarsi station was going to be replaced by the railway authorities next year. — Incorrect. “Was going to” is in the past. The active “are going to” is in the present.

Option 4: The old foot overbridge at Itarsi station are going to be replaced by the railway authorities next year. — Incorrect. “Are” agrees with the authorities. But the new subject is “the old foot overbridge”, which is one, so it needs “is”.