As agriculture spread, farmers adapted plants to new environments. Maize arrived in eastern North America in about 300 B.C.E., but remained a minor crop for another thousand years until women there developed a strain that produced high yields in climates with as few as one hundred frost-free days per year.

maize

The word “strain” in the passage is closest in meaning to? 


留下评论

您的电子邮箱地址不会被公开。 必填项已用 * 标注