下列浅表软组织感染的概念，不正确的是（）。

A.疖是指单个毛囊及其皮脂腺的急性化脓性感染

B.痈是指多个相邻的毛囊及其皮脂腺的急性化脓性感染

C.急性淋巴管炎是指淋巴管阻塞导致的急性化脓性感染

D.丹毒是指皮肤及其网状淋巴管的急性化脓性感染

E.急性蜂窝织炎是指皮下、筋膜下、肌间隙或深部蜂窝组织的一种急性弥漫性感染

Which of the following statements about duration and convexity is FALSE（）

A. duration to first call is longer than duration to maturity.

B. convexity of a callable bond is always lower than that of a noncallable bond when rates fall.

C. callable bonds’ convexity can be negative.