阿摩線上測驗
9. The focal length of a camera lens is 20.0 cm. How far from the lens should the subject for the photo be if the lens is 20.5 cm from the film?
(A) 8.20 m
(B)4.10 m
(C) 2.10 m
(D) 6.30 m
(E) 10.0 m
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統計： A(40), B(3), C(1), D(0), E(2) #2020468
統計： A(40), B(3), C(1), D(0), E(2) #2020468
