Seeing photos of a trip to the beach your friends didn't invite you to can really be upsetting.
该句是一个含有定语从句的主从复合句。
主句：Seeing photos为主语，而of a trip to the beach为后置定语（修饰前面的photo），can be是系动词（短语），upsetting是表语，really是状语。
定语从句（修饰beach）中，your friends是主语，didn't invite是谓语，you是宾语，to (which/that)是状语。
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第1个回答 2020-09-06
Seeing photos of a trip to the beach
(非谓语动词结构doing作主语，两个介宾短语作后置定语)
(that/which) your friends didn't invite you to
(定语从句，引导词在从句中作宾语省略)
can really be upsetting.
(非谓语动词结构doing作主语，两个介宾短语作后置定语)
(that/which) your friends didn't invite you to
(定语从句，引导词在从句中作宾语省略)
can really be upsetting.
