单项选择题 Why does the technology has become a competitive area？ A、change speeds B、extend the driving range C、the pressure of cut cost D、increases power efficiency

单项选择题 FA022多仓混棉机的混合原理是同时喂入，不同时输出。（    ） A、正确 B、错误

单项选择题 The formal salutation in a certificate to the recipient is ______. A、To whom it may concern, B、My dear friend, C、Dear Mr. Smith, D、Dear Sir / Madam,