C. 10 m/s
You divide 1000 m by 100 s.
1000/100 to find the velocity
Main sequence stars are characterised by the source of their energy.They are all undergoing fusion of hydrogen into helium within their cores. The mass of the star is the main element for such process or phenomenon to take place for it is a determinant of both the rate at which they perform the said activity and the amount of fuel available.
To answer the question, the lower mass limit for a main sequence star is about 0.08. If the mass of a main sequence star is lower than the above-mentioned value, there would be a deficit or insufficiency of gravitational force to generate a standard temperature for hydrogen core fusion to take place and the underdeveloped star would form into a brown dwarf instead.
Answer:
A. 
B. t = 50 s
Explanation:
A. The vectorial equation of the person who is getting closer to the other person is:

r: position vector
v: speed vector = 6m/s i (if you consider the motion as a horizontal motion)
Then, you replace and obtain:

B. The time is:

d: distance to the observer = 300m
v: speed of the person on the car = 6.00 m/s

Answer: A) Wavelength and frequency are inversely proportional.
Explanation:
From the wave equation;
Velocity= frequency × wavelength
If the above equation is rearranged making the frequency the subject of formula, it would give;
Frequency= velocity/ wavelength.
From the above equation we see that frequency is inversely proportional to the wavelength. This means that for every increase in wavelength there would be a decrease in frequency, and for every increase in frequency there is a reduction in wavelength.