句子功能題（function of the sentence）屬于ACT語法中特有的一種題型，出題形式是在文中劃線，題目一般問如果把文中劃線部分去掉，段落會失去什么。

例子：

We have long known that ancient Egyptians sailed the freshwater Nile River. However, until Wadi Gawasis was excavated, there had been little evidence that [3] we had also sailed the ocean. [B] Hieroglyphic inscriptions suggested that some of the excavated objects had been used in an expedition to the ancient Red Sea port of Punt about one thousand miles from Wadi Gawasis. Planks pocked with holes bored by shipworms, [4] creatures that live only in salt water, supported the hypothesis that ancient Egyptians had ventured into the ocean.

4. If the writer were to delete the underlined portion (adjusting the punctuation as needed), the paragraph would primarily lose an explanation of why:

F. evidence of shipworms could indicate that the Wadi Gawasis ships had sailed the ocean.

G. archaeologists thought Punt was the destination of the Wadi Gawasis expedition.

H. shipworms may have bored holes in the planks of the Wadi Gawasis ships.

J. there was evidence of shipworms at Wadi Gawasis.

答案解析

此題選F。首先原文中劃線部分是前面shipworms一詞的同位語，如果不看劃線部分Planks pocked with holes bored by shipworms…supported the hypothesis that ancient Egyptians had ventured into the ocean. 意思是船板上布滿了船蟲鉆出的洞，這支持了古埃及人曾冒險進入海洋的假設，那么讀者很容易產生疑問：為何有這些洞就能證明古埃及人到過海洋呢？因此劃線部分其實提供了一種解釋，即這些船蟲只生活在鹽水中，由此可以判斷出F選項正確。句子功能題一定要把劃線部分結合上下文的語境判斷，干擾項往往只含有一些相關用詞但從邏輯上看并不成立，因此比較容易排除。