He_______tostudyharderinthefuturesothathecouldhavemoreopportunitiestofindabetterjob.
Whenmakingmoderncameras,peoplebeganto_______plasticsformetal.
Students with _______ problems may apply for student loans.
All the memories of his childhood had _______ from his mind by the time he was 65.
It is not ---_______ for me to return all the books to the library now because I still need some of them for my research.