It turns out that many materials can be solid at a higher temperature if the pressure is also higher. so even though it is hotter in the inner core the pressure in the core is also higher and you can have a solid iron nickel instead of liquid
The answer should be the third option "number of protons and neutrons." The atomic mass of a element is equal to the amount of protons, and neutrons added together in that element. So for example if we are trying to find the atomic mass of hydrogen you would add the total amount of protons and neutrons together to find it's mass although it doesn't equal the exact amount of it's mass but it's close.
Hope this helps.
<span>After the third month of development, lanugo develops on the head (thin, first hair), the muscles and bones are formed an shaped, the mouth movement is possible, the liver and pancreas produce fluid secretions, meconium is made (stool of infant), reproductive organs are developed, but the baby's gender is difficult to distinguish on ultrasound.</span>
The second and third one I believe
