A florist wants to determine if a new additive would extend the life of cut flowers longer than the original additive. The florist selects the first 20 carnations from the ones recently delivered by the greenhouse and assigns the first 10 to the new additive and the rest to the original additive. After three weeks, 6 carnations placed in the new additive still looked healthy, and 2 carnations placed in the original additive still looked healthy. The proportion of healthy carnations with the new additive was significantly greater than the proportion of healthy carnations with the original additive.

Which of the following is a valid conclusion?

It can be inferred that the new additive caused the extended life of the cut flowers, and this inference can be applied to all carnations.
It cannot be inferred that the new additive caused the extended life of the cut flowers, and this inference cannot be applied to the carnations from the greenhouse.
It can be inferred that the new additive caused the extended life of the cut flowers, and this inference can only be applied to the carnations from the greenhouse.
It cannot be inferred that the new additive caused the extended life of the cut flowers, and this inference can only be applied to the carnations from the greenhouse.