Adding fractions is difficult.

Each element of this set has a unique characteristic.

Learning how to use past participles is important for understanding English.

This sentence is very long.

He is our boss.

He worked late into the night to complete his doctoral thesis.

I am solving integration problems in math class.

He is majoring in liberal arts at university.

On the day of the vernal equinox, I went to the park to feel nature.

The autumnal equinox is the day when the length of day and night is almost equal.