Arock has 12.5 percent of its original amount of potassium-40 remaining in it; potassium-40 has a half-life of 1.25 billion years. how long ago was the rock formed?

a) 1.25 billion years ago

b) 2.5 billion years ago

c) 3.75 billion years ago

d) 5 billion years ago

the answer is b) 2.5 billion years.  if its half life is 1.25 billion years and there is only 25% of the element remaining, you would take 1.25 billion and multiply it by two to get 2.5 billion.

the child will have heterozygous dominant chromosomes as characters of his father are dominant over the characters of his mother.

the child is heterozygous