A nurse is reinforcing teaching about infant car seat use with a group of new parents. Which of the following instructions should the nurse include in the teaching?

"You should place a folded blanket to pad the back of the infant's head."

"You should position the car seat at a 30-degree angle."

"You should use a car seat with a four-point harness."

"You should place the retainer clip at the level of the infant's armpits."