Which of the following is most useful to scientists in measuring the size of asteroids?

the speed at which the asteroid is traveling.
the location of the asteroid in the solar system.
the gravitational effect when spacecraft flies close to the asteroid.
the composition of the asteroid.

i don't know the answer to this

for many centuries there were important factors which the economies of the muslim empires developed increasingly. they applied economic procedures in production, investment, finance, taxation and property. they used to tax certain goods (for example: harvest), they charged interest on money lent, they signed contracts with merchants; they relied on a common currency, and they used checks as well as promissory notes. with the money collected by means of taxation, the government provided the needy with an income. in addition, trading networks covered huge distances, so far regions started to have contact and exchange goods. this trade network covered areas of asia, africa and europe.