Question

my sister _ bought a new car ( have, has)​

Answer 1

hey mate!!!!

my sister has bought a new car

Answer 2

My sister has bought a new car.

The present perfect tense is formed by have/has+ the past participle, where the first element depending on the subject is has or have and the second is the past participle form of the verb. This tense basically indicates an action that has occurred at an indefinite time in the past (e.g., I have met him before) or an action that has begun in the past and still continuing in the present (e.g., His fever has grown over the last hour). But you cannot use this tense when you are specified about when the action happened.