What must be present in order for people to be considered a social group?
a. similar incomes b. common interests c. different ages d. varied languages

Option B, Common interest

Explanation:

A social group is a set of people that share common characteristics, views and interests. All the members of any social group have common goals and objectives which brings high sense of unity and solidarity among its members.  There are several social groups in the society based on caste, religious or ethnic beliefs, gender, groups with vested interest , In & Out groups etc.  

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."

the correct answer is b