Which of these hydrocarbons has a double bond in its carbon skeleton?
a. c3h8
b. c2h6
c. ch4
d. c2h4

(i don't know how to find out if their is a double bond based on the molecular formula)

Select all the true statements about the cosmic microwave background radiation

The eruption of a nearby volcano causes a prairie ecosystem to receive a lot less sunlight. which of these is the most likely effect on the ecosystem? a-an increase in biodiversity. b-an increase in immigration to the area. c-a decrease in available water. d-a decrease in plant growth.

How does the nervous system affect the excretory system?