The best evidence that shows that the trait in the pedigree chart is a recessive trait is couple 3-4 in the 2nd generation producing children who do not show the trait.
The father (3) is affected for the trait but the mother is not. However, none of the children is affected. This means that the allele inherited from the mother by the children is able to mask the effects of the affected allele they inherited from their father.
If the allele they inherited from their father is not recessive, definitely the children should have been affected by the trait. Hence, the trait is expressed by homzygous recessive alleles.
More on recessiveness can be found here: https://brainly.com/question/18075358
