A
The cost of collecting and disposing of general trash has been less than the cost of collecting and disposing of recyclables, and this is still likely to be the case under the new recycling program.
B
Even if the volume of collected recyclables increases, that increase might not be enough to make the recycling program cost effective.
C
Because the volume of recyclables people accumulate during a week is less than what they accumulate during two weeks, the city expects a recyclables pickup to take less time under the new program.
D
A weekly schedule for recyclables pickup is substantially easier for people to follow and adhere to than is a schedule of pickups every other week.
E
Because of the increase in the number of pickups under the new program, the amount charged by the contractor that collects the city’s recyclables will increase significantly.
A
Some students who did not participate in the chess program had learned to play chess at home.
B
Those children who began the program but who did not successfully complete it had lower preprogram levels of achievement than did those who eventually did successfully complete the program.
C
Many of the children who completed the program subsequently sought membership on a school chess team that required a high grade average for membership.
D
Some students who did not participate in the chess program participated instead in after-school study sessions that helped them reach much higher levels of achievement in the year after they attended the sessions.
E
At least some of the students who did not successfully complete the program were nevertheless more talented chess players than some of the students who did complete the program.
Researchers working in Western Australia have discovered the oldest fragments of the Earth’s early crust that have yet been identified: microdiamonds. These microscopic crystals measure only 50 microns across and were formed 4.2 billion years ago. This discovery sheds light on how long it took for the Earth’s crust to form, since this date is only 300 million years after the formation of the Earth itself.
Summary
Western Australian researchers have discovered microdiamonds, the oldest fragments of the Earth’s early crust yet identified. These microscopic crystals were formed 4.2 billion years ago, only 300 million years after the formation of the Earth itself. This discovery sheds light on how long it took for Earth’s crust to form.
Notable Valid Inferences
Earth’s crust did not take longer than 300 million years to begin to form.
A
The Earth’s crust took no longer than 300 million years to start to form.
Must be true. We know this because the microdiamonds researchers found were part of the Earth’s early crust. If the microdiamonds existed 300 million years after Earth itself was formed, then Earth’s crust must have taken no longer than 300 million years to begin to form.
B
The Earth’s crust first formed in the area that is now Western Australia.
Could be false. To claim this is where the Earth’s crust first formed is too extreme. We only know that the microdiamonds the researchers found are the oldest fragments to be found to date. It is possible there exists older fragments that have not yet been found.
C
The Earth’s crust took billions of years to form.
Must be false. We know the microdiamonds the researchers found were part of Earth’s early crust, and these existed only 300 million years after the formation of Earth.
D
Microdiamonds were the first components of the Earth’s crust to form.
Could be false. To claim microdiamonds were the first components is too extreme. We only know that they are the oldest fragments identified to date. It is possible that older fragments exist that have not yet been identified.
E
All naturally occurring microdiamonds were formed at the time the Earth’s crust was being formed.
Could be false. To claim all microdiamonds were formed at this time is too extreme. It is possible that there are other naturally occurring microdiamonds that formed after the ones the researchers identified.