You have three layers of skin which act as a barrier against diseases.
這個(gè)句子本來(lái)就是定語(yǔ)從句.我不知道樓主哪里看到說(shuō)這個(gè)是賓語(yǔ)從句的.
這個(gè)句子主謂賓都有：You have three layers of skin.這就是個(gè)完整的句子,后面which引導(dǎo)就是個(gè)定語(yǔ)從句,來(lái)修飾three layers of skin,并且which做從句的主語(yǔ).
給你舉2個(gè)賓語(yǔ)從句的例子,你就明白這兩種句子的不同了.
I don't know （where he is from）.我不知道（他從哪兒來(lái)）
I think （that you are right）.我認(rèn)為（你是對(duì)的）.
括號(hào)內(nèi)為賓語(yǔ).這就是賓語(yǔ)從句.