China made a commitment to the world in the Copenhagen Summit that by 2020, the carbon-intensity of its economy ______ fall 40% to 45%.
A.shall | B.may | C.must | D.should |
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China made a commitment to the world in the Copenhagen Summit that by 2020, the carbon-intensity of its economy ______ fall 40% to 45%.
A.shall | B.may | C.must | D.should |