The major organ of the circulatory system, the heart

Yes the heart is the major organ of the circulatory system it's main function is to propel blood throughout the body.

the diploid number of chromosomes is sometimes represented by the symbol 2n. for the fruit fly, the diploid number is 8, which can be written as 2n = 8, where n represents twice the number of chromosomes in a sperm or egg cell.

idk what the options are but

these is a strong electrostatic attraction between the ions hence a lot of energy is needed to overcome this attraction

this is why the boiling points are so high