He hasn't visited his grandparents for a few days --> The last time..........................................................

Answer: The last time he visited his grandparents was a few days ago.

`-` Chuyển từ hiện tại hoàn thành `->` quá khứ đơn

`-` The last time + S + V-ed/C2 + O + was + khoảng thời gian + ago.

`-` Lần cuối cùng anh ấy đến thăm ông bà là cách đây vài ngày.

$#tr$

Công thức đổi HTHT - QKĐ

S + has/have + not + V3/ed + for/since + time 

--> S + last + V2/ed 

--> The last time + S+ V2/ed + was + time 

--> It is / has been + time + since + S+ (last) + V2/ed 

----------------------------------------------------

Đáp án: The last time he visited his grandparents was a few days ago.

`color{orange}{~LeAiFuRuiHuiBao~}`