NTRCA ফুল মডেল টেস্ট১৯৭টি পরীক্ষায় এসেছেপ্রশ্ন ২৬Which of the following sentences is correct?কOne of the problems is very difficult to solve.খOne of the problems are very difficult to solve.গOne of the problem is very difficult to solve.ঘOne of the problem are very difficult to solve.উত্তর দেখুন