Answer: If the mother is deaf and has an X-linked recessive allele, she must have two copies of the mutant allele (one on each X chromosome). Since men only have one X chromosome, they cannot be carriers of the allele. Therefore, if the father has normal hearing, he must have two normal alleles.
In this case, all of the sons will inherit a normal allele from the father and a mutant allele from the mother, making them deaf. However, none of the daughters will be deaf since they will inherit one normal allele from the father, which will override the mutant allele on the X chromosome inherited from the mother.
Therefore, the correct answer is: All of the sons will be deaf and all of the daughters will have normal hearing.
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