The direct object pronoun would be "la" because la gasolina is feminine. In a sentence you could say
La compro en la estacion de servicio.
Direct object pronouns are placed before the verb generally.
The letter in the Spanish alphabet is silent and not pronounced when speaking Spanish is H.
The correct answer is B. 7.5 liters because 13.5/67.5=.2
It literally takes points just for no one to answer you and if someone does it’s too late