A decade has gone by since they __________ from high school.

• Since এর প্রথম অংশ Present Indefinite/ Present Perfect Tense হলে পরের অংশ Past Indefinite Tense হয়। 
• আবার Since এর প্রথম অংশ Past Indefinite Tense হলে পরের অংশ Past Perfect Tense হয়। 
যেমন: 
- Many years have passed since his father died. 
- It was many years since they had first met. 

• প্রদত্ত বাক্যে since এর প্রথম অংশ A decade has gone by হচ্ছে Present Perfect Tense, তাই পরের অংশ Past Indefinite Tense হবে।
- নিয়মানুযায়ী সঠিক উত্তর - A decade has gone by since they graduated from high school.