Approximately how many years has agriculture contributed to the growth and development of civilization? *

explanation:

the sun shines white and black light to our planet. the white light has all the colors in it. in our upper atmosphere, we have dust particles and oxygen molecules. the white light meaning all of the colors in a rainbow shines through the upper levels of the atmopshere and the blue light scatters across the entire planet. that is why our sky is blue.

bradycardia ( blood presssure below 120/80mmhg )

it is contraindicated to give nitroglycerin to patients with blood pressure that is lower than normal range because the drug can cause blood pressure to drop further. it can lead to paradoxical bradycardia and less commonly, threatening hypotension.