Question

Choose the phrase that best completes this sentence

Answer 1

I believe the answer should be D. En voz alta. 
En voz alta means aloud in English, so if you say:
No puedo oir tus palabras. Necesitas hablar en voz alta.
In English it would mean:
I can not hear your words. You need to talk out loud.
~I hope this is able to help you. Good day.~

Best regards~ Sans

Answer 2

D. En voz alta meaning in a louder voice