The genetic makeup of an individual plays a vital role in determining their susceptibility to certain diseases.

This can't be done by individual effort.

prior to lightning strike, describe where and how the charges build up

The sky was gray and cloudy.

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The ratio of boys to girls in the class is 2:3.

This is the single most important decision of your life.

I'm learning English.

The farmer pitched the hay onto the wagon.

The two lines are parallel to each other.