Why is the claim of the discovery of microfossils controversial?
A) they are found in rocks from the Hadean Eon
B) it is not clear whether they are of biological or mineral origin
C) the rocks they are found in are probably contaminated by terrestrial bacteria
D) they are too small to be of biological origin
B
You might also like to view...
Slanting Surfaces With Friction: A block of mass m sits at rest on a rough inclined ramp that makes an angle ? with the horizontal. What must be true about normal force F on the block due to the ramp?
A. F > mg B. F > mg cos ? C. F > mg sin ? D. F = mg cos ? E. F = mg sin ?
Now click the second tab (labeled "Terrestrial Planet Temperatures"), then explore what happens as you click the button that allows you to add or remove greenhouse gases. Which terrestrial planet would have its surface temperature the most dramatically changed if its greenhouse gases were removed from its atmosphere?
a. Venus b. Mars c. Mercury d. Earth
A certain light source blinks once per second in its own frame of reference. As you recede from the blinking source, you observe the frequency of blinks to be
A) less than 1 Hz. B) 1 Hz. C) more than 1 Hz.
A series LR circuit includes a 9.0 V battery, a resistance of 0.20 
and an inductor. When the switch is closed, the circuit exhibits a time constant of 200 ms. What is the inductance of the circuit?
A. 42 mH B. 15 mH C. 32 mH D. 40 mH E. 22 mH