What worried the child most was _____________ to visit his mother in the hospital.

A．to his being allowed

B．his not being allowed

C．not his being allowed

D．not his allowed

抑制免疫过程多个环节：

A．胸腺素

B．干扰素

C．环孢素

D．糖皮质激素类

E．左旋咪唑