Read these sentences and fill in the gaps with the verb 'can'. Example 0. She swim well. Answer 0. can. 1. You take a taxi if you want. 2. Walter and Kitty ride a bike. 3. John go to the concert if he has free time.

1. You can take a taxi if you want.
To fill in the gap, we use the verb 'can' because it indicates the ability or possibility of taking a taxi. This means that you have the option or permission to choose a taxi as a mode of transportation if you desire or need it.

2. Walter and Kitty can ride a bike.
In this sentence, we use the verb 'can' because it shows the ability or skill of Walter and Kitty to ride a bike. They have the capability to ride a bicycle without any issues or difficulties.

3. John can go to the concert if he has free time.
Here, we use the verb 'can' to express the possibility or opportunity for John to attend the concert. Whether he can go or not depends on his availability and whether he has any free time. If he does have spare time, then he has the ability or option to go to the concert.