It would be D. Stratified due to the fact that it couldn't possibly be any of the others. It isn't random because it is only women, Cluster isn't correct either, a cluster would mean "random" people which is the same as different people in a small group. It isn't Convenience due to the fact that "Convenience wouldn't even make sense in this situation. Lastly, Systematic and stratified are really close but one would still be more logical than the other.
Since each min is 60 seconds you multiply 60 by the number of minutes which is 7 and you get 420:
60x7=420 Then you add 30 seconds equaling 450 seconds total
Then you divide 450 by 4 since she ran 4 laps.
So, Stephanie ran 112.5 seconds per lap
In order to convert scientific notation to standard form, just move the decimal over however many places the exponent is. In this case you move it positively (to the right) 8 places to get 175,000,000
6 because it is the greatest number that both can be divided by