Most likely the students are using a crude measurement of time, like a stopwatch. They would get the best results with a scientific apparatus that uses a computer and optical sensors. Even recording their dropped objects with a video camera and analyzing the video would give more consistent results. Results will also vary greatly if different people are taking the time measures instead of one person making all measurements.
The correct answer is A. Nebula, star of seven stellar masses, a red supergiant, supernova, black hole.
Explanation
Stars have a life cycle that begins with the gravitational collapse of a gaseous nebula. Subsequently, thermonuclear fusion occurs that allows the conversion of hydrogen into helium, this causes the released energy to pass through the star and radiate in a phase called the star of seven stellar masses. After several billion years, the star passes to the "red giant" stage. Here the star contracts and raises its temperature. After this, the stars (which have masses greater than the sun) detach from their layers forming supernovae, and later, these give rise to "black holes". According to the above, the correct answer is A. Nebula, star of seven stellar masses, a red supergiant, supernova, black hole.
The Sun's outer gases extend far beyond the photosphere (Figure 6). Because they are transparent to most visible radiation and emit only a small amount of light, these outer layers are difficult to observe. The region of the Sun's atmosphere that lies immediately above the photosphere is called the chromosphere.
Methamphetamine is neurotoxic to dopaminergic neurons in the human’s midbrain. It increases the amount of the dopamine in the brain and as a result, produces the euphoria feeling that many people experience. It is also indicated that high-dose methamphetamine use can be neurotoxic to serotonin neurons (with the potential of damaging neurons)<span>.</span>