Explanation:
The sentence given is
No pueden ___ la computadora portátil
which translates to
They cannot _____ the laptop.
We want to fill in the blank. Usually, the infinitive verb can come right after a conjugated verb.
Pueden is the verb poder conjugated for ellos/ellas/ustedes. Since it is already conjugated, we can use the answer choice B. abrir because it is the infinitive (not conjugated).
The complete sentence is
No pueden abrir la computadora portátil
which translates to
They cannot open the laptop.