The ability to roll the edges of the tongue upward in a U-shape has been considered to be an inherited ability. The standard assumption is that tongue-rolling is a dominant allele at a single
gene locus. Which of the following would cast doubt on this assumption?
A. A teacher reports that after testing her class on the ability to roll their tongue, with very little
effort the non-tongue-rollers can learn to also roll their tongues.
B. A student who can roll his tongue has a mother and father, both of whom cannot.
C. A student who cannot roll his tongue has a mother and father, both of whom can.
D. Both A and B are situations that would cast doubt on this assumption.

D. Both A and B are situations that would cast doubt on this assumption

they are:

A. A teacher reports that after testing her class on the ability to roll their tongue, with very little effort the non-tongue-rollers can learn to also roll their tongues.

B. A student who can roll his tongue has a mother and father, both of whom cannot.

Explanation:

A traits is a special characteristics  or qualities that is common to an organism. it is usually passed down/ inherited from parents to offspring or as a result of environmental factors. some traits that are inherited from parents cannot be inherited from the environment those are genetically inherited characteristics.

Tongue rolling is a simple genetic traits that is capacity of an individual to roll the lateral edges of the tongue upwards into a tube. it is inherited from one parent.

The  option A and B contradicts  as it is not a learn characteristics but an inherited trait. and student can only role his/her tongue if one of the parent has that special ability to role the tongue and if that trait was passed to that child. so a student cannot possess that ability to roll the tongue if their parents do not have it.