14. While we _____ at the beach, we saw dolphins swimming nearby.
(A) relax
(B) relaxing
(C) had relaxed
(D) were relaxing
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統計: A(2), B(9), C(17), D(67), E(0) #3440474
統計: A(2), B(9), C(17), D(67), E(0) #3440474