【正确答案】 D

【答案解析】[理由] 原句实等于：
Those(1) who are taking part in the ultra marathon in Arizona next month(2) are advised to carry a first-aid kit(3), which should include a remedy for snakebites.(4)
1) 为主语。
2) 关系代词who引导的定语从句，可将who are省略而成为taking part in引导的分词短语。
3) are advised to carry a first-aid kit则为其陈述部分。
4) 关系代词which所引导的部分为定语从句，用来修饰先行词a first-aid kit。
由以上分析得知，因为句首有主语Those，故空格中应填入动词。
由于advise(建议；劝告)是及物动词，之后应有动名词或that从句作其宾语。之后若无宾语时，则应使用被动语态，即is/are advised(被建议；被劝告)，因此(D)应为正选。
[例] I advise doing the work now.
(我建议现在就做这工作。)
I advise that you do the work now.
=You are advised to do the work now.
(我建议你们现在就做这工作。)