$\text{11.}$ is helping - does

$\text{→}$ now chia HTTD

$\text{→}$ often chia HTD

$\text{12.}$ did they spend - don't know - think - were

$\text{→}$ last summer chia QKD

$\text{13.}$ are you going - am going

$\text{→}$ Wait! chia HTTD

$\text{14.}$ do you swim 

$\text{→}$ How often chia HTD

$\text{15.}$ did - dressed - had

$\text{→}$ yesterday chia QKD

$\text{16.}$ was - could

$\text{→}$ kể lại QK chia QKD

$\text{17.}$ is swimming

$\text{→}$ Look! chia HTTD

$\text{18.}$ are learning

$\text{19.}$ didn't work - was

$\text{→}$ last month chia QKD

$\text{20.}$ does he usually get up - gets up - is still sleeping - painted - got

$\text{→}$ usually và always chia HTD

$\text{→}$ today chia HTTD

$\text{→}$ yesterday chia QKD