中国大学MOOC: Which of the following ensembles doesnt contain the cello?

Which of the following ensembles doesn't contain the cello? A: Piano trio B: Big band C: Orchestra D: String quartet

Erhu sometimes known in the West as the_______,is a two-stringed bowed musical instrument and is used as a solo instrument as well as for small ensembles and large orchestras. The most popular erhu piece is Two Springs Reflect the Moon.