Sodium-24 has a half-life of 15 hours. How much of a 20 mg sample would remain after
two half-lives?

away from the curb

explanation:

the wheels would then hit the curb if it started to rolling, decreasing the chance of an accident.

d.) circle motion requires a force to give it a centripetal acceleration.

explanation: no but i do not usually comment

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.