The half-life of protactinium-226 is 2 minutes if you started with 20 grams of pa-226 how much do you have after 8 minutes

Divide the amount in half for every 2 minutes

0 minutes = 20 grams

2 minutes = 20/2 = 10

4 minutes = 10/2 = 5

6 minutes = 5/2 = 2.5

8  minutes = 2.5/2 = 1.25 grams

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms

well the answer is 2!