Explanation:
1 and 17 are highly reactive bc they are almost full or not full at all. they need there last shell to be full in order to be happy, or not reactive. 18 has the noble gases which are not reactive at all bc they have a full valence shell and dont need any other electrons.
C. calcium is your answer
Answer:
The hydrogen bond between complementary nucleotides (C)
Explanation:
Hope this helped
<span>D) Vaccines allow for building immunity without harmful exposure because not all viruses are safe to be exposed to.</span>
