The correct answer is: A. Was completed
The sentence is in the past tense, so the verb must be in the past tense as well. Option A is the only option that is in the past tense.
Option B is in the present progressive tense, which is used to describe actions that are happening now or that are happening repeatedly. Option C is in the past progressive tense, which is used to describe actions that were happening at a specific time in the past. Option D is in the future tense, which is used to describe actions that will happen in the future.
The new railway bridge was completed two weeks ago. This means that the action of completing the bridge happened at a specific time in the past. Therefore, the correct verb tense to use is the past tense.