Which words help you to determine the meaning of the word declerate in paragraph 3 ?

There is nothing attached to the question but this is the definition.

verb (used with object), de·cel·er·at·ed, de·cel·er·at·ing. to decrease the velocity of: He decelerates the bobsled when he nears a curve. to slow the rate of increase of: efforts to decelerate inflation.

Edit: reduce or cause to reduce in speed.

"the train began to decelerate"

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.

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.