Answer:
The answer is below
Explanation:
The half life of a substance is the time required by that substance to reduce to half of its initial value. The half life is calculated using the formula:

Given that t = 87 years, half life = 29 years, therefore the quantity of strontium-90 left is:

That is one-eight of Strontium 90 would be left after 87 years
Answer:
i believe its B but i might be mistaken.
Explanation:
Flatworm<span>, also called platyhelminth, any of the phylum Platyhelminthes, a group of soft-bodied, usually much flattened invertebrates. A number of </span>flatworm<span> species are free-living, but about 80 percent of all </span>flatworms<span> are parasitic—i.e., living on or in another organism and securing nourishment from it.</span>