单选题 Like any other (constant) repeated action, speaking (has to) be learned, but once it (is learned), it becomes a generally (unconscious) and apparently automatic process.

A、 constant
B、 has to
C、 is learned
D、 unconscious

【正确答案】 A

【答案解析】应改为constantly，因为修饰repeated，应用副词形式。