Answer:
One building block
Explanation:
The prefix mono means one
<span>Melanin helps protect the skin against effects of the sun such as skin cancers and premature aging. In African American skin, melanin provides a sun protection factor (SPF) equivalent to 13.4 compared to 3.4 in white skin and thus the former have lower incidences of skin disorders associated with exposure to the sun.</span>
Hydrogen because it only has one valence electron I believe.
Because the common cold is cause by a ‘virus’.......
The answer is VIRUS
