Explanation:

Correct option is 4: 'amazed'.
The most appropriate word for the given blank is 'amazed'.
The word 'amazed means very surprised. 
 Example: I was amazed by the change in his behaviour.
The given sentence is talking about a past incident and the whole of the sentence is in the past tense.
Hence, a simple past helping verb should be used.
Correct Sentence: The agility of the acrobat amazed and thrilled the audience.