Gregor Mendel performed a cross between a pure-breeding tall plant and a pure-breeding short plant. He observed that the resulting offspring were all tall. Given this information, it can be inferred that: the allele for tall plants is recessive and none of the offspring received an allele for short height.

the allele for short plants is dominant and all of the offspring received an allele for tall height.

the allele for tall plants is dominant and all of the offspring received at least one allele for tall height.

the offspring were all pure-breeding like the parent plants.