What major external cue outside the labratory resets our internal clocks to a 24-hour day?

What do you call a star with 5 points? Can 1 over 18 be reduced? When do you use a semi colen? A person who accepts nothing less than excellence is? What day in week was the queens coronation? What number must you add to complete the square x2 plus 4x equals 5? How many acute angles does a 5 pointed star have? What does the name Taloria mean? Would you use grams or kilograms to weight a glass? Who invented the H-R diagram? What is the slope 2x plus 3y plus 6 equals 0? What is log of 0.2? Is 6432 divisible by 10? What is 2 086 374 in words? Who prepares the PERET diagrams who is responsible for their integration? What will drop first a big ball or a small ball? How do you calculate radius to volume ratio of a sphere? What is a 2 step equation that equals 7? How do you write 0.49735 in word form? What shape doesn't have right angles?