$\text{37.}$ I wish I could swim across the river .

→ Câu ước của "can" : S + wish(es) + (that) + S + could + V-inf 

$\text{38.}$ Helen has learnt Chinese since 2010.

→ started/began + to V/V-ing → has/have + Vpp 

$\text{39.}$The telephone was invented by Bell in the nineteenth century.

→ Bị động thì Quá Khứ Đơn : S + was/were + Vpp + ( by O ) 

$\text{40.}$My uncle asked me when my school vacation started .

→ Câu tường thuật dạng Wh-? : S + asked + sb + Wh-? + S + V(lùi thì ) + O 

→ Hiện Tại Đơn → Quá Khứ Đơn 

$\text{#Yang Heun}$

37. I wish I could swim across the river 

câu ước ở tương lai 

38. Helen has learnt Chinese since 2010 

HTD-> HTHT 

39. The telephone was invented by Bell in 19 century 

40. My uncle asked me that when  my school vacation started

câu tường thuật