your friends great-grandmother speaks only mandarin how can you communicate with her?

A speak english
B speak loudly
C dont speak at all
D smile and nod

The best option would be to A. speak English. Even if the great-grandmother does not understand English, speaking slowly and using simple words may help her to grasp the basic meaning of what you are saying. Additionally, you can use gestures and body language to supplement your communication. However, it is also beneficial to learn a few basic Mandarin phrases or commonly used words to establish a basic level of communication and show respect towards her language and culture.