SNP is a single nucleotide polymorphism. It means that a particular sequence varies among the members of a population with respect to the single nucleotide. The given sequence of the human genome is "AATGGAGTC". The sequence "AATGGAGTT" of option C differs from it with respect to the single nucleotide at the last position (C is replaced with T).
Similarly, the sequence of option D "AATAGAGTC" differs with respect to the nucleotide at position 4 (G in the original sequence is replaced with A). Therefore, these two sequences represent SNP with respect to the given sequence of the human genome.
Clubfoot describes a range of foot abnormalities usually present at birth (congenital) in which your baby's foot is twisted out of shape or position. In clubfoot, the tissues connecting the muscles to the bone (tendons) are shorter than usual.