他一眼就认出了她，因为她正在向朋友们挥手。
He recognized her at once because she was waving at her friends.
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because英 /bɪˈkɒz/|美 /bɪˈkɔz/
was英 /wɒz/|美 /wɑz/
waving英 /ˈweɪvɪŋ/|美 /ˈweɪvɪŋ/
解释
用过去进行时 `was waving` 解释认出对方的原因，because 引出理由。
He recognized her at once because she was waving at her friends.
用过去进行时 `was waving` 解释认出对方的原因，because 引出理由。