The correct answer is (a) excessive heat. Death Valley is the hottest place on Earth, with an average annual temperature of 77 degrees Fahrenheit (25 degrees Celsius). The highest temperature ever recorded on Earth was 134 degrees Fahrenheit (57 degrees Celsius), which was recorded in Death Valley on July 10, 1913.
Option (b) is incorrect because Death Valley is not known for its excessive cold. The average annual low temperature in Death Valley is 41 degrees Fahrenheit (5 degrees Celsius).
Option (c) is incorrect because Death Valley is not known for its abnormal depth. The average elevation of Death Valley is 282 feet (86 meters) below sea level.
Option (d) is incorrect because Death Valley is not known for its excessive salinity. The average salinity of the water in Death Valley is 10 parts per thousand.