30. Grammar: Choose one best answer.
(A)Tungsten, a gray metal with the melting point is the highest of any metal, is used to form the wires in electric light bulbs.
(B)Biochemists use fireflies to study bioluminescence, the heatless light given off by certain plants and animals.
(C)June bugs they often cause damage by stripping the young leaves from trees and shrubs.
(D)The latest Flash Mob event involved a large number of people invaded a shoe boutique, all noisily pretending to be out-of-towners on a bus tour.