1. Most of us never ask ourselves if and how television might hurting us.
2. Most never ask themselves if and how television might hurting them.
3. Most never ask themselves if and how television might hurting us.
.....
Which ones are grammatically correct?
All three need to say, "might BE hurting us". Otherwise, all are correct.
One could also say, "how television hurts us." "hurting" is a gerund, a noun. A verb is needed.
Out of the three sentences you provided, only the second one is grammatically correct:
2. Most never ask themselves if and how television might be hurting them.
Here's why:
In sentence 1, the word "hurting" is not used correctly. The correct form would be "hurt," as it needs to be in the present tense to match the rest of the sentence. Additionally, the pronoun "us" in the latter part of the sentence should also be changed to "them" to match the subjects mentioned earlier.
In sentence 3, the pronoun "us" is incorrectly used in the latter part of the sentence. If the sentence is referring to the majority of people, the correct pronoun to use is "them."
Therefore, only the second sentence is grammatically correct:
2. Most never ask themselves if and how television might be hurting them.