When you have some difficult math problems,you can ____ your math teacher.

We work together to achieve our common purpose: __________ world that is safer, cleaner and healthier than __________ one we are living in.

Which city has _____ population, Dongying, Shanghai or Jinan

Sixty miles ________ in a single night, so they were exhausted

The boy,____ with his school work every day. felt rather tired and wanted to have a whole day to relax.