阿米巴痢疾的大便性状为
A．柏油样便
B．粘液性脓性鲜血便
C．暗红色果酱样脓血便
D．洗肉水样血便
E．米泔水样便
参考答案：C
My brother _____ a tennis racket.[ ]
A. have
B. don't have
C. doesn't have
D. doesn't has
说明次级代谢及其特点。如何利用次级代谢的诱导调节机制及氮和磷调节机制来提高抗生素的产量？
