1 . Read the sentences and explain why the passive voice is used.
1. A total of 28 men had been selected out of the applicants before Ernest Shackleton set out for Antarctica.
2. It is said that South Georgia had never been crossed by explorers on foot before Shackleton and his men’s expedition.
3. On 17 January 1915, the Endurance got stuck in ice. A lot of efforts were being made to solve the problem when the ice melted and the ship suddenly broke in half.

2 . 根据语境，选择下框中的单词或短语换句中划线部分的单词或短语，必要时用正确的形式，使之意思一致。

imply        assess        demonstrate        employ       distinguish       witness     interact

1. When we think about nonverbal behavior, or body language, we think about communication.
2. Modern methods of tracking polar bear populations have been used only since the mid-1980s.
3. In Japan, it may display respect to look down when talking to an older person.
4. In a sense, it’s human nature to judge the advantages and disadvantages of decisions all the time.
5. Several journalists saw the incident happen in which eight people were injured.
6. The teacher’s smile suggested that she had forgiven the students.
7. An open-source discussion makes it challenging for users to recognize the difference between truth and rumors.