Select the correct answer.

A disease-resistant variety of a sexually reproducing crop was planted on a field with an existing non-resistant variety. After a few years, pests severely attacked the plants. The older, non-resistant plants died. However, the recently grown plants survived. Why did the new plants survive?

A. The pests can't attack the new plants.
B. The new plants had the resistant gene.
C. The old plants were covered with low-grade insecticides.
D. The new plant variety was younger than the initial plants.
E. The recently grown plants had an increased life span.