—Lucy doesn’t seem to be what she was.

—No. ____so much in the war has made her more thoughtful.

A．Seen

B．Her seeing

C．Having seen

D．To have seen

在光电效应实验中，某金属的截止频率相应的波长为λ₀，该金属的逸出功为________．若用波长为λ(λ<λ₀)的单色光做该实验，则其遏止电压为________．已知电子的电荷量、真空中的光速和普朗克常量分别为e、c和h。