Final answer:
The missing words in Javier's sentences are 'pelotas' and 'varios'.
Step-by-step explanation:
Based on the options given, the missing words can be chosen as follows:
Voy a jugar al tenis con..
The correct answer would be pelotas as Javier is going to play tennis.
Ayer yo compré..
The correct answer would be varios as it means 'several' and can refer to the items Javier bought.
Therefore, the completed sentences would be:
Voy a jugar al tenis con pelotas.
Ayer yo compré varios.
Learn more about Completing sentences in Spanish