Which answer choice shows the best way to introduce a sentence that summarizes or explains the information before it?

Marissa will be a huge help. She is going to organize the children to spread the soil in the new gardens.

Marissa will be a huge help, she is going to organize the children to spread the soil in the new gardens.

Marissa will be a huge help: she is going to organize the children to spread the soil in the new gardens.

Marissa will be a huge help: She is going to organize the children to spread the soil in the new gardens.

The best way to introduce a sentence that summarizes or explains the information before it is: "Marissa will be a huge help. She is going to organize the children to spread the soil in the new gardens."