The key to the evolution of altruism is that a. recipients have to be more likely to carry the altruistic allele than nonrecipients. b. actors have to be more likely to carry the altruistic allele than nonactors. c. recipients have to be unrelated to the actors. d. nonrecipients have to be more likely to carry the altruistic allele than recipients.

The correct answer is b. actors have to be more likely to carry the altruistic allele than non actors.

Explanation:

Altruism is the behavior by an organism that benefits other organisms by costing its own fitness. The actor is the individual who is doing altruism and the recipient is the individual who is getting benefited by the actor's altruism.

An example of altruistic behavior can be seen in animal kingdom easily. Vampire bats give blood to those members of the community who were not able to go for search for blood show altruistic behavior.

Actors have altruistic genes that suggest them to behave altruistically. Non-actors may not contain alleles of altruism but the recipient might have altruistic alleles.

Hamilton's rule says that natural selection will favor the altruistic allele when rb > c.

where r = coefficient of relatedness between donor and recipient

          b = benefit received by recipient and

          c = cost paid by altruist.

Therefore, the correct answer is b.

halogen, any of the six nonmetallic elements that constitute group 17 (group viia) of the periodic table. the halogen elements are fluorine (f), chlorine (cl), bromine (br), iodine (i), astatine (at), and tennessine (ts).

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

hope this