It’s difficult _____ your sound because thenoise is too high.

October 1, 1949 was the day ________ the People’s Republic of China was founded．

Tom talked with a friend of _______ on the Internet for a long time yesterday.

Zheng He had over 300 ships, _______ some were over 150 meters long and could carry up to 1,000 people.

Tim got up late this morning, _______ he hadto go to school by taxi.