— Coach,can I continue with the training?

— Sorry, you can't ______you haven't recovered from the knee injury.[ ]

A. unitil  

B. before

C. to consider  

D. unless

男性，78岁，肺癌，发热，寒战，皮肤广泛瘀斑，考虑存在DIC，应用肝素治疗，肝素抗凝的主要机制是

A．抑制凝血酶原的激活

B．抑制因子X的激活

C．促进纤维蛋白吸附凝血酶

D．增强抗凝血酶田活性

E．抑制血小板聚集