Answer:
1. Voy a hacerla.
2. Necesitamos llevarlos.
3. Marcos lo está pidiendo / Marcos está pidiéndolo.
4. Javier debe llamarlos.
5. Ellos desean visitarlo.
6. Puedo llamarlo por la mañana.
7. Prefiero llevarla.
8. No queremos perderlas.
Explanation:
It is called a direct object (in traditional grammar, direct complement) to the function played by a syntactic constituent (phrase, pronoun or a substantive subordinate proposition), different from the grammatical subject, which is necessarily required by a transitive verb
It is the person or object on which the action expressed by the verb falls, it is a modifier of the predicate. The direct object can be expressed by pronouns: lo, la, los, las. Substituting the direct object of a sentence for one of these pronouns is a recommended way to verify that it is indeed the direct object.
