例句 1：She placed the letter carefully inside the envelope.
例句 2：He handed me a sealed envelope and asked me not to open it until tomorrow.
例句 3：The job offer came in a plain white envelope.
例句 4：Please write your return address on the back of the envelope.
例句 5：The envelope was marked “Confidential” in red ink.
例句 6：We’re pushing the envelope with this new design—it’s bold and innovative.
例句 7：Don’t forget to put a stamp on the envelope before mailing it.
例句 8：The budget envelope for this project has already been exceeded.