If one has 24 kg of polonium and it undergoes two half-lives, how much do you have left?

What makes the results of a scientific experiment accurate? a) having multiple trials b) lacking any supporting data c) working in a lab d) using a hypothesis that is always true

1. seamount a raised footwall block between normal fault creates this 2. syncline break between rocks where a hanging wall rises relative to a footwall 3. hot spring on rolling hills, this a dip between hills 4. volcanic neck created when a block with hanging walls slips down between normal faults 5. caldera underwater volcano that never reaches above sea level 6. horst natural hot water on earth's surface containing many minerals 7. graben underwater volcano whose top is eroded flat by waves 8. crater less than a mile in diameter; looks like a bowl at the top of a volcano 9. guyot magma that filled the central vent that remains after the volcano has eroded 10. reverse fault over 1 mile in diameter; looks like a bowl over a volcano

Which of the following was not a major animal on land during the carboniferous period? amphibians insects both a and b none of the above