Ex4: 
1. It is about 300km from HCM City to Phu Quoc Island.
2. Traffic rules should be obeyed strictly by road users.
3. If you are not careful, you'll hurt yourself.
4. The flowers are watered every day.
5. It takes me two hours to do my homework.
Ex5: 
1. Ba is playing the guitar and listening to music in the room.
2. Would you like to come to my house for dinner?
3. They will be learning English this time tomorrow.
4. My brother doesn't like ice-skating because he thinks it is dangerous.
5. People won't use flying cars until year 2050.