decrease, reduce and decline

[sjc55]

Dear teachers,

1. What is the difference among "decrease" ,"reduce" and "decline"?
In the following sentence, which word would be acceptable?

"The death rate on the road has decreased 40% after the law was enforced."

2. Should I use "active" or "passive" voice of the word?

[Offroad]

They both work.

It was reduced/decreased by 40%.

[not a teacher]