题目内容：

    One day, gardeners might not just hear the buzz of bees among their flowers, but the whirr of robots, too. Scientists have managed to turn an unassuming drone (无人机) into a remote controlled pollinator (授粉媒介) by attaching horsehairs coated with a special, sticky gel to its underbelly.

Animal pollinators are needed for the reproduction of 90% of flowering plants and one third of human food crops. Chief among those are bees — but many bee populations in the United States have been in steep decline in recent decades. Thus, the decline of bees isn’t just worrisome because it could disrupt ecosystems, but also because it could disrupt agriculture and economy. People have been trying to come up with replacement techniques, but none of them are especially effective yet.

Scientists have thought about using drones, but they haven’t figured out how to make free-flying robot insects that can rely on their own power source without being attached to a wire. “It’s very tough work,” said senior author Eijiro Miyako, a chemist at the National Institute of Advanced Industrial Science and Technology. His particular contribution to the field involves a gel, one he’d considered a mistake 10 years before and stuck in a storage cabinet. When it was rediscovered a decade later, it hadn’t dried up or degraded at all. “I was so surprised because it still had high viscosity,” Miyako said.

The chemist noticed that when dropped, the gel absorbed an impressive amount of dust from the floor. Miyako realized this material could be very useful for picking up pollen (花粉). He and his colleagues chose a drone and attached horsehairs to its smooth surface to mimic a bee’s fuzzy body. They coated those horsehairs in the gel, and then controlled the drones over lilies, where they would pick up the pollen from one flower and then deposit the pollen at another one, thus fertilizing it.

The scientists looked at the hairs under a scanning electron microscope and counted up the pollen grains attached to the surface and found that the drones whose horsehairs had been coated with the gel had about 10 times more pollen than those that had not been coated with the gel.

Miyako does not think such drones would replace bees altogether, but could simply help bees with their pollinating duties. There’s a lot of work to be done before that’s a reality, however. Small drones will need to become more controllable and energy efficient, as well as smarter, with better GPS and artificial intelligence.

1.What does the underlined word “viscosity” in Para.3 probably mean?

A.Hardness. B.Stickiness.

C.Flexibility. D.Purity.

2.We can learn from the passage that______.

A.bees disrupt both agriculture and economy

B.scientists have invented self-powered robot insects

C.bees in the United States are on the edge of extinction

D.Miyako found the special feature of the gel by chance

3.According to Eijiro Miyako, the drones______.

A.are not yet ready for practical use

B.may eventually replace bees in the future

C.are much more efficient than bee pollinators

D.can provide a solution to economic depression