Select the elements that have 4 valence electrons. hydrogen (H)

krypton (Kr)

strontium (Sr)

carbon (C)

oxygen (O)

tin (Sn)

Ineed to know why d is the correct answer asap

Fan egg cell containing the (n+1) number of chromosomes combines with a sperm cell containing the (n) number of chromosomes, what is the result of this union? a) all future somatic cells of the organism will contain the (2n + 1) number of chromosomes. b) all future somatic cells of the organism will contain the (2n - 1) number of chromosomes. c) only certain somatic cells of the organism will contain the (2n + 1) number of chromosomes. d) all future somatic cells of the organism will contain the normal diploid number of chromosomes.

Plz will mark! the diagram shows the positions of the sun, moon and earth during spring tides, when the high tides are at their highest and low tides at their lowest. what is it about these positions that causes these high and low tides?