Which pair of words correctly completes this sentence?

yo sé pastel de manzana, cocino para el cumpleaños de mi madre y mi hermana.
cocino, lo
cocinar, lo
cocinar, las
cocinar, la

This is a sentence written in present tense with the 1st person in singular yo (I). This is also a case of a verbal periphrasis or verbal phrase using the verb saber (to know) and generally is written in a sentence as follows:

Here the verb saber is conjugated in present as sé (I know) and according to the context of the sentence and following the explanation above, we must use the verb cocinar (to cook) in infinitive.

On the other hand, the element that directly receives the action of the verb is pastel de manzana (apple pie), which is the direct object of this sentence.

Now, after the end of the coma, pastel de manzana is substituted by the direct object pronoun lo.

This pronoun is in accordance in number and gender with the direct object pie de manzana, which is the 3rd person in singular it.

Finally, the complete and correct sentence is:

I know how to cook apple pie, I cook it for the birthday of my mother and my sister