You are designing a schema for a table that will be moved from MySQL to Cloud Bigtable. The MySQL table is as follows: 

How should you design a row key for Cloud Bigtable for this table? 

Answer options:

A. Set Account_id as a key.
B. Set Account_id_Event_timestamp as a key.
C. Set Event_timestamp_Account_id as a key.
D. Set Event_timestamp as a key.

C