为以下程序填空,使得输岀结果是{40:'yuwen’,20:'yingyu' ,30:'shuxue'}的选项是__________。tb = {'yingyu':20, 'Shuxue':30,'yuwen':40}stb ={}for it in tb.items ():print(it)________________print (stb)
A. stb[it[1]]=tb[it[0]]
B. stb[it[1]]=tb[it[1]]
C. stb[it[1]]=it[0]
D. stb[it[1]]=stb[it[0]]