To our ears, it sounds as if an echo: A. is louder than the original sound.
O B. is at a higher pitch than the original sound.
C. comes from the surface on which the sound wave reflected.
D. comes from the location of the original sound.

the answer is true. hope it .

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.

i think tornado but not 100%