A well-tested explanation that explains a lot of observations is:

explanation:

allergens: overstimulate the nerve system

neurotics: attack nerve cells

mutagens: damage or otherwise alter dna sequence

generators: cause defects during growth and development  

carcinogens: cause unchecked cell growth

i hope you get the idea according to me these are the effects that happened.

hello

question:

when would a new household be started?

a.when the oldest male died

b.when a man and a woman married

c.when the house could not hold everyone

d.when a child was born

answer: us d when a child was born

hope this have a great day and brainlest

answer; biological;