The people who create the IELTS reading tests do so by paraphrasing parts of the passage for each question. In other words, they choose a word or phrase in the passage that they want to test you on, and they write a question using words which have a similar meaning.
The table below shows the similar words from last week's exercise:
The words highlighted in blue were the correct answers because the same meaning was expressed in the passage and the question.
The phrases in black do not express exactly the same meaning (e.g. the fact that climbers have died does not mean that it is the most dangerous mountain). These answers were therefore wrong.