If roundworms are removed from the soil and placed in a liquid, they thrash helplessly around.

单项选择题Medieval cities grew rapidly when they had harbors nearby.

单项选择题Due to the tilt of Neptune’s axis, the Sun heats the planet’s northern and southern hemispheres unequally.

单项选择题At first glance, a forest appears to be a haphazard collection of trees, shrubs, vines, and flowers.

单项选择题Modern nursing practices not only hasten the recovery of the sick but also promote better health through preventive medicine.

单项选择题Because of Delaware’s lenient laws regarding business incorporation, many companies have their headquarters in the state’s largest city, Wilmington.