Which statement is FALSE concerning precautions during fueling operations?（）

A.All engines，motors，fans，etc. should be shut down when fueling

B.All windows，doors，hatches，etc. should be closed

C.A fire extinguisher should be kept nearby

D.Fuel tanks should be topped off with no room for expansion

脐血是新生婴儿脐带被结扎后由脐带流出的血，其内含有大量的造血干细胞。下面有关叙述不正确的是（）

A.从免疫学角度分析，脐血自身移植的优点是排斥反应小

B.干细胞的功能特点说明它具有一定的全能性

C.由造血干细胞形成淋巴细胞的过程实质是基因的选择性表达

D.造血干细胞通过有丝分裂就可以形成人体各种细胞