Two quick questions
prefiero una carta.
a. escribas
b. escribe
c. escribi
d. escribo

la agente de viajes recomienda que nosotros
a. llevar
b. llevabamos
c. llevamos
d. llevemos

The right option in each case is:

- Prefiero que escribas una carta.

- La agente de viajes recomienda que nosotros llevemos.

Explanation:

The translation of the sentences is:

- I'd rather you write a letter.

- The travel agent recommends that we carry.

In Spanish there is a mode of conjugation called Subjunctive, which usually uses hypothetical actions or that have not yet occurred to mention wishes or suggestions, although this mode belongs to the Present Tense, its conjugation varies with respect to the Present Simple Affirmative, as shown by continuation with the verbs "escribir" and "llevar:"

How the tacit noun in the first sentence is "tú," the right conjugation is "escribas," and how the personal pronoun in the second sentence is "nosotros," the right conjugation is "llevemos."