Suppose Jim and Tom can both produce baseball bats. If Jim’s opportunity cost of producing baseball bats is lower than Tom’s opportunity cost of producing baseball bats, then A: Tom must have an absolute advantage in the production of baseball bats. B: Jim must have an absolute advantage in the production of baseball bats. C: Tom has a comparative advantage in the production of baseball bats. D: Jim has a comparative advantage in the production of baseball bats.

中国大学MOOC: Suppose Jim and Tom can both produce baseball bats. If Jim’s opportunity cost of producing baseball bats is lower than Tom’s opportunity cost of producing baseball bats, then

—Do you have ping－pong bats? —________， and I have baseball bats, too.

Why is social interaction between bats so difficult to study according to Dr. Kate Barlow A: Because bats are sneaky. B: Because bats have diurnal habits. C: Because bats are small and have nightly habits. D: Because bats can listen out for competitors’ feeding buzzes.

Which is true referring to Mexican freetail bats? A: The Mexican freetail bats under the bridge eat a lot of beneficial insects every day. B: The Mexican freetail bats live under the Congress Avenue Bridge all the time. C: The Mexican freetail bats are easy to infect rabies to people. D: Only when the Mexican freetail bats are in danger can they bite people.

“目光如豆” is similar to the American idiom describing people who are as blind as bats.

Bats communicate___each other by ultrasonicmessages.

How can you prevent bats from entering your house A: By blocking every opening B: By planting bushes near the doors C: By training your dog to hunt bats D: By using poison to kill the bats

It is suspected that the covid-19 is _____by bats. A: transplanted B: transformed C: transported D: transmitted

What might be the cause of the bats' collisions?（ ）