胚胎第5月时主要造血器官是

A．卵黄囊
B．胆囊
C．淋巴管
D．肝脾
E．骨髓

待测粉末与硫酸共同振摇，过滤，以硫酸冲洗滤器。（）

A．Shake the powder being examined with chloroform, filter and reserve the extracted powder.

B．Shake the powder being examined with chloroform, filter and evaporate almost to dryness on a water bath.

C．Heat the powder being examined with a mixture of water and hydrochloric acid in a water bath.

D．Heat the powder being examined to boiling with a mixture of ethanol and water.

E．Shake the powder being examined with sulphuric acid, filter and wash the filter with sulphuric acid.