The correct answer is B.

Explanation: The sentence "Although I am watching television, I ____________ what you are saying." requires a verb phrase that indicates the ability to perceive sound while engaged in another activity.

- B. can hear is correct because it shows that despite watching television, you are able to hear what is being said. "Can hear" indicates a present ability to perceive sound.

Other options:
- A. am hearing: This implies an ongoing action and is not typically used to describe the ability to perceive sound.
- C. have heard: This refers to something that has been heard in the past, not necessarily indicating the ability to hear while currently engaged in another activity.
- D. was hearing: This is past continuous and does not fit with the current situation of watching television and listening simultaneously.

Thus, "can hear" is the best choice to complete the sentence.