Questions 19 to 22 are based on the passage you have just heard. What is the ovenbird’s nest made of

A．Clothing stores where people are relaxed and off guard.
B．Hotels and restaurants in southeast London.
C．Airports where people carry a lot of luggage.
D．Theater lobbies with uniformed security guards.

A．the current in one place is not strong enough to give a shock
B．the fish’s electric cells are filled with jelly like substance
C．to complete the circuit, you have to touch the fish in two places
D．a torpedo’s electric cells contain more than one electric plates