C. Está cosa es un lápiz amarillo
Los papeles is the plural version of paper in Spanish:
it is answer C.
Those are the options you have? or did you write them
Anyway
11: entender
12:pensar
13:Preferir
13:empezar
15:almorzar
16:volver
17:dormir
18:encontrar
19:pierde
20:querer