The Riemann sum is a method for approximately calculating the integral of a function.

His performance is generally good.

He followed the footprints left on the snow.

He was appointed as the chief executive officer of the company.

I saw a Canada goose in the park.

He closed his eyelids and took a deep breath.

This area is rich in schist.

I add a little rock salt to this dish to enhance the flavor.

In ancient Japan, the 方相 played an important role.

Shale is one of the main sources of oil and gas.