I believe c. I hope it helps :)
Answer:
The corona shines only about half as brightly as the Moon and is normally not visible to the unaided eye, because its light is overwhelmed by the brilliance of the solar surface. During a total solar eclipse, however, the Moon blocks out the light from the photosphere, permitting eye observations of the corona.
Answer:
The heat capacity of the calorimeter or of the reaction mixture may be used to calculate the amount of heat released/absorbed by the chemical reaction. The amount of heat released or absorbed per gram or more of the reactant can then be calculated from the mass of the reactants.
-Quinn
The time measured by a stopwatch is not an exact number. The number is limited by the precision of the instrument (the stopwatch) and it migh have been 56.004 instead of 56.00, and the stopwatch cannot shoe that. So, this is not an exact number.