$\text{ĐÁP ÁN+GIẢI THÍCH:}$
$\text{10. THEY LAST WENT ON A PICNIC WAS MANY MONTHS AGO}$
$\textit{S+LAST+O+WAS+TIME+AGO}$
$\text{11. SHE HAS WORKED AS A SECRETARY FOR FIVE YEARS}$
$\textit{S+HAS/HAVE+V3/ED+FOR+YEAR}$
$\text{12. I'VE BEEN WORKING FOR THE COMPANY FOR A YEAR}$
$\textit{S+HAS/HAVE+BEEN+V_ING}$
$\text{13. THIS IS THE FIRST TIME I HAVE EATEN THIS KIND}$
$\textit{THIS IS THE FIRST TIME+S+HAVE/HAS+V3/ED}$
$\text{14. IT'S A WEEK SINCE THEY LAST CLEANED THE STREETS}$
$\text{15. AFTER HE HAD LIVED IN HANOI FOR 10 YEARS, HE MOVED TO HCM CITY}$
$\textit{AFTER+S+PAST PERFECT, S+V2/ED}$
$\text{16. IT'S YEARS SINCE I ENJOYED MYSELF SO MUCH}$
$\text{17. IT'S HOURS SINCE THE TELEPHONE RANG}$
$\text{18. IT'S OVER 6 MONTHS SINCE JOHN LAST HAD HIS HAIR CUT}$
$\text{19. IT'S YEARS SINCE THEY LAST STAYED IN A HOTEL}$
$\text{20. IT'S 5 YEARS SINCE I LAST SAW HER}$
$\text{21. IT IS THE FIRST TIME I HAVE READ THIS BOOK}$
$\textit{IT IS THE FIRST TIME+S+HAVE/HAS+V3/ED}$
$\text{22. IT IS THE FIRST TIME MY FATHER DROVE A CAR}$
$\text{23. THE LAST TIME I SAW HIM WAS AUGUST AGO}$
$\text{24. THE LAST TIME I PLAYED FOOTBALL WAS 1970 AGO}$
$\textit{THE LAST TIME+S+V2/ED+WAS+YEAR+AGO}$
$\text{25. TOM HAS PLAYED THE PIANO FOR 4 YEARS}$
$\textit{S+HAS/HAVE+V3/ED+FOR/SINCE+YEAR}$