You're asking a question about parallelism in lists. This comes up on the GMAT quite often.

Here's a correct sentence:

At the zoo, I saw a giraffe, a zebra, and an elephant eating lunch.

Here is another correct sentence:

At the zoo, I saw a giraffe, zebra, and elephant eating lunch.

In the first sentence, I put an article next to every item in the list. In the second sentence, I put an article in front of the first item only. Either one is acceptable.

The same is true for auxiliary verbs attaching to several main verbs in a list:

At the game, the opening pitch was thrown, caught, and given to fan.
At the game, the opening pitch was thrown, was caught, and was given to a fan.