Despite his efforts, he failed the exam.

Feudalism characterized the social system of medieval Europe.

Changes in the social system inevitably occur with time.

Slavery is something that robs human dignity and is absolutely unacceptable.

We believe that a reform of the education system is necessary.

He supports anarchy.

Kaku is my best friend.

He is proficient in calculating quadrature in astronomy.

He is struggling to understand the ablative case in Latin.

The sum of one angle of this triangle and its complementary angle is 90 degrees.