Answer (3) is the most correct, although (2) is not to be ignored. (3) states the most abundant isotope Ti's average mass, which is certainly true. (2) is the total mass of all protons, neutrons, and electrons in an atom of Ti, which is true but has to be more specific in order to pinpoint exactly the 47.88 amu. (4) is incorrect because it is not of all the naturally occurring isotopes of Ti. (1) is incorrect because they forgot electrons.
Answer: Convection Currents
Explanation: The mantle rock is solid and denser because it is cooler. This means it will sink closer to lower mantle as warmer, lense dense rock/magma moves upwards.
Atomic number should be the answer
A spring - also an electromagnet. Also know as a slinky!