B. "the nameless grace/Which waves in every raven tress" is correct.
The possible outcomes are Tt and tt.
An isolated colony on a selective medium is not considered a pure culture because inhibited organisms might be masked by the colonies. This statement is true.
On the basis of their constitution or usage, culture media can be classified into various groups; these include defined, complex, selective, as well as enrichment medium.
A selective medium consists of dyes or noxious substances/chemicals which inhibit the growth of specific microorganisms but promote the growth of other microbes.
A pure culture is a laboratory culture which contains a single species of microorganism. It is free from other microorganisms.
Since selective media affects the growth of distinct organisms differently, therefore, an isolated colony formed in such type of medium is not considered a pure culture.
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A chemical change is a change in which the composition of the matter is changed at the molecular level, most chemical changes are not easily irreversible, for example, an egg being cooked, the egg changes from its liquid like state to a solid, and it is not possible to revert it back to its original change. The egg itself is changed in this case.
A physical change on the other hand however, is only changing the substance of a matter, not its composition, this is usually easily reversible. For example, water turning into ice, the water's substance changed from its liquid state to its solid state, it is still water, and it can easily be turned back into water by heating it.
Sorry for the long explanation,
Hope this helps!
