You are given a paragraph, a question and some answer options (associated with "A", "B", "C", "D", etc.) You need to list all the correct answer options with their associated letters (e.g. "A" can be a valid answer). Note that sometimes, more than one option can answer the question correctly and completely. In those cases, please generate all such options separated by a comma (e.g. "A, B" is a valid answer). Do not generate anything else apart from one or more of the following characters: 'A', 'B, 'C', 'D', etc.

[EX Q]: Paragraph- Sent 1: The inhabited history of the Las Vegas Valley stretches to 23,000 b.c.
Sent 2: , when much of the area was covered by a prehistoric lake.
Sent 3: During this period, the indigenous people lived in caves, hunting the mammals that gathered at the shoreline.
Sent 4: The landscape of the valley changed dramatically over the next 200 centuries.
Sent 5: The glaciers feeding the lake melted away and the lake evaporated.
Sent 6: Fossils tell an obscure story of man's slow and sporadic development.
Sent 7: Around 3000 b.c.
Sent 8: , native Archaic Indians began to develop a lasting hunting and gathering culture.
Sent 9: By this time, the valley was in much the same geographic state as it exists in today, with one exceptionthe presence of artesian springs that bubbled to the surface in several areas.
Sent 10: These springs fed a network of streams draining through the Las Vegas Wash to the Colorado River.
Sent 11: The areas surrounding the springs were desert oases: sprawling collections of grasses, trees, and wildlife.
Sent 12: Many springs lay in areas that would eventually become the center of the modern Las Vegas metropolis.
Sent 13: For about 4000 years, the Archaics thrived in a culture that included many signs of early civilization.
Sent 14: Signs of even more advancement appeared halfway through the first millennium a.d.
Sent 15: , when the Anasazi Indians inhabited the valley.
Sent 16: Far more progressive than the Archaics, the Anasazi utilized such formal agricultural techniques as irrigation to assist their harvest.
Sent 17: This permitted the Anasazi to achieve a benchmark of advanced societythe ability to live in permanent shelters year-round without need to follow wildlife.
Sent 18: Mysteriously, the Anasazi vanished from the valley around a.d.
Question: Approximately what year was the Las Vegas Valley covered by a prehistoric lake? (A) 23,000 b.c (B) 1500 b.c (C) Around 3000 b.c (D) 2000 b.c.
[EX A]: A.

[EX Q]: Paragraph- Sent 1: Tropical climates are found around the equator.
Sent 2: These climates have warm temperatures year round.
Sent 3: Tropical climates may be very wet or wet and dry.
Sent 4: Tropical wet climates occur at or very near the equator.
Sent 5: They have high rainfall year round.
Sent 6: Tropical rainforests grow in this type of climate.
Sent 7: Tropical wet and dry climates also occur near the equator.
Sent 8: They receive less rainfall.
Sent 9: Most of the rain falls in a single season.
Sent 10: The rest of the year is dry.
Sent 11: Few trees can withstand the long dry season.
Sent 12: The main plants are grasses.
Sent 13: Dry climates receive very little rainfall.
Sent 14: They also have high rates of evaporation.
Sent 15: This makes them even drier.
Sent 16: Deserts can get less than 25 centimeters of rain per year.
Sent 17: Thats less than 10 inches per year.
Sent 18: How much rain do you get at your house?.
Question: Which climates have warm temperatures year round? (A) Tropical (B) Climates near the equator (C) Deserts (D) Season climate (E) Tropical climates (F) Sub-tropical (G) Climates near north and south poles.
[EX A]: A, B, E.

[EX Q]: Paragraph- Sent 1: Density is also an important physical property of matter.
Sent 2: The concept of density combines what we know about an objects mass and volume.
Sent 3: Density reflects how closely packed the particles of matter are.
Sent 4: When particles are packed together more tightly, matter is more dense.
Sent 5: Differences in density of matter explain many phenomena.
Sent 6: It explains why helium balloons rise.
Sent 7: It explains why currents such as the Gulf Stream flow through the oceans.
Sent 8: It explains why some things float in or sink.
Sent 9: You can see this in action by pouring vegetable oil into water.
Sent 10: You can see a colorful demonstration in this video.
Question: Do differences in density influence the phenomenon that occurs when pouring vegetable oil into water? (A) No (B) Yes.
[EX A]:
B.