42. Many countries are increasing their use of natural gas, wind and other forms of ________.
If you are ________ about Australia cities, just read the book written by Dr. Johnson.
Mr. White will come to the party on Sunday, _______ he promised to every one of us.
Mary has recently got engaged ________ a foreign teacher, who has been engaged ________ education research for years.
Time ________ quickly. Three years passed before we knew it.
Mr. Smith is busy these days ________ a new book on how to develop a child’s reading skill.