Before they are actually sent up in a spacecraft，______(宇航员需经受各种各样的测试)．

A．John gave everyone a big surprise yesterday.
B．Everyone wore casually at the wedding party.
C．John did not read the dressing code on the invitation letter.
D．Everyone except John dressed formally at the wedding party.

A．controlling the Latino population
B．enhancing the educational level of the Latino population
C．improving the knowledge-based economy
D．building the Latino population into hardworking and skilled workforce