4) According to the studies cited in the articles you just read, how much greater is the current extinction rate than the average background extinction rate of the last 542 million years?
A. 0-5 times greater than the background rate
B. 5-10 times greater than the background rate
C. 50-75 times greater than the background rate
I
D. 100-1000 greater than the background rate
E. 100,0000-1,000,000 times greater than the background rate

As a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is 100) a) static friction. b) kinetic friction. c) a combination of static and kinetic friction. d) neither static nor kinetic friction, but some other type of friction. e) it is impossible to tell what type of friction acts in this situation.

Astone is dropped from the upper observation deck of a tower, 250 m above the ground. (assume g = 9.8 m/s2.) (a) find the distance (in meters) of the stone above ground level at time t. h(t) = (b) how long does it take the stone to reach the ground? (round your answer to two decimal places.) s (c) with what velocity does it strike the ground? (round your answer to one decimal place.) m/s (d) if the stone is thrown downward with a speed of 2 m/s, how long does it take to reach the ground? (round your answer to two decimal places.) s

Estimate of the number of stars in our galaxy