In what year did the us and several other nations agree to reduce the quantity of cfcs used by 50%?

2017

1987

2007

1997

I think 1987 sorry if wrong have a great day

1987

Explanation:

The depletion of the ozone layer and the antarctic ozone hole made a danger for the humans to survive on the planet. Depletion of the ozone from the continued use of CFCs can cause skin cancer and many problems which dragged international action to be implemented.

Thus, in 1987, around 56 countries agreed the Montreal Protocol which states the CFC production to cut and also reduction of its use to half.

After few years, this protocol was more strengthened to stop the worldwide production of CFCs and also other chemicals which depletes ozone layer.

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.

sorry, but you do not have posted the diagram.