Although medical science __________ control over several diseases,what worries us is that some of them are returning.

A．achieved

B．has achieved

C．will achieve

D．had achieved

“打倒列强，除军阀”；“星星之火，可以燎原”；“将革命进行到底”。上述口号所反映的历史发展主题是

A．工农武装割据

B．新民主主义革命

C．抗击外来侵略

D．推翻国民政府