to be struck dumb and unable to utter a word; to be tongue-tied and speechless
面对大家的疑问，他感到有些心虚，箝口结舌，不知如何回答。
Facing everyone's questions, he felt a bit guilty, tongue-tied, and didn't know how to answer.
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to be struck dumb and unable to utter a word; to be tongue-tied and speechless