MYSQL Group Replication
You can't configure a MySQL server to connect to multiple masters as a replication slave.

You can configure Master B with log_slave_updates enabled, Master A with binlog_format = ROW and declare table 2 using Engine=BLACKHOLE on Master B, and the replication events from Master A's binary log will cascade through Master B onto Slave C, which would be connected only to Master B (not directly to A).

Otherwise, your alternative is Multi-Source Replication in MariaDB, which (unlike Oracle MySQL) does allow a single server to connect to multiple upstream masters simultaneously, as long as there are no conflicting combinations of schema+table names being replicated.  This configuration should work whether the master servers are actually running MariaDB or if they're running MySQL.