23. Speed of cars is measured ________kilometres per hour.
Without enough food, many birds didn’t ________ the winter.
---Sorry, I’ve got an important appointment at 9 o’clock and I can’t _______ to miss it.
Little Tom was so enthusiastic about learning Chinese and after six months, he could speak it ______ fluently.
This is a complex operation. A team of nurses _____ the doctor in performing the operation.
The conflict between economic development and environmental protection, if not appropriately _________, can cause disastrous consequences in daily life settings.