Ludmila's child was born with an extra chromosome, resulting in down syndrome. this is most likely an example of a(n)

This is most likely an example of a mutation.

Mutation is any alteration or change in DNA sequence which affects the genetic instruction carried by that gene. Mutation can occur either as a result of errors during DNA replication or due to environmental factors such as cigarette smoke and ultraviolet (UV) radiation. Mutations are heritable, especially if they have a positive effect. The disorder Down syndrome is an example of mutation which occurs due to error in cell division in which there is extra copy of a genetic material (specific chromosome); chromosome 21.

d. a slower response to a stimulus and sustained without fatigue.

Explanation:

The activity of the enzyme ATPase is slower in the smooth muscles as compared to the skeletal muscles as a result the production of ATP is also slow this can directly affect the response giving ability of the smooth muscles to the stimulus so there is an delay in the response given by the smooth muscles. The smooth muscle cells are involuntary. They use very little amount of ATP does during energy requirements they sustain without fatigue.