dark matter may explain
a. unexpected orbital velocities of stars in galaxies
b. the source of energy that fuels stars
c. the expansion of the universe
d. the origin of life
e. what came before the big bang

and dont you dare say e.

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees. 

the best answer for these questions would be:

1.            c. is smaller

2.            d) concrete operational

3.            b) interaction with the environment – the children interact with their environment can them learn more.

4.            a) parents who reason openly with children can limit a child’s cognitive ability.