Answer : 2. "We were surprised about her failure to get admission in the Science stream."
Explanation :

In Active Voice, a sentence emphasizes the subject, performing an action.
In Passive Voice, a sentence emphasizes the action or the object of the sentence.
The given sentence is in the active voice and 'her failure' is the subject and 'us' is the object.
When we convert this sentence into passive voice, the subject 'her failure' of the active voice becomes the object, the object 'us' becomes the subject 'we'.
The passive format "were + V3 (surprised)" should be used.
This is the active and passive voice rule for the past simple tense.
Hence, the correct answer is option 2.