Very heavy elements such as gold and uranium are formed by a) Loss of neutrons
b) Supernova Explosion
c) Hydrogen burning in small stars
d) Nuclear splitting

i think   the answer is c hope i'm right

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.

it’s previous models   because when i picked that son of a gun’s answer it was wrong look for previous models because they might make it a different letter  

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.