At the head of the procession _______, each holding a red flag in his or her hand.

A．the Young Pioneers marched

B．marched the Young Pioneers

C．did the Young Pioneers march

D．where marched the Young Pioneers

下列物质中对骨髓所有造血细胞的增殖、分化都有调控作用的是()

A．G-CSF

B．IL-2

C．IL-3

D．IL-4

E．IL-6