He will spend six hours at his desk _______ he finishes his composition.

In some countries such as France or Italy, it’s common to exchange a kiss when shaking hands, ______ in China, it’s not acceptable.

  It is uncertain ________ side effect the medicine will bring about, although about two thousand patients have taken it.(2010·浙江)

____ we are alone, we can speak freely.

 As a matter of fact, ________ matters most in learning English is enough practice.