Which of these is the best method to measure the distance to a star?

calculate the variations in the position of the star due to movement of earth in its orbit
measure the red shift of emitted light and use it in calculations
use doppler effect to calculate the shift in light traveling from star to earth in summer
use doppler effect to calculate the shift in light traveling from star to earth in winter

Why does lightning travel from clouds to the ground?

Ineed this now one scientist feels that the changes in global climatic patterns may be good for the health of the biosphere. another scientist feels that sharp changes in climatic patterns could result in the extinction of the biosphere. which of these is the most likely reason the two scientists gave conflicting opinions on the impact of changes in the global climatic pattern? they do not have enough knowledge on the topic. they did not discuss the issue among themselves. they believe conflicting opinion strengthens science. they study different areas of science and have different scientific focuses.

How long will it take a car traveling of a constant speed of 45m/s to cover the distance of a 2.5km?