1．(2019年北京卷·阅读理解C)A lot of business is still done over the phone, and much of it is ________ (base) on trust and existing relationships.
2．(2019年北京卷·阅读理解C)Voice manipulation technologies may weaken that ________ (gradual).
3．The news of his appointment filtered out before it was ________ (official) advertised.
4．American ________ (use) differs from that of English in certain ways.
