Final answer:
Humans can theoretically survive with one extra chromosome, specifically if it's one of the smaller chromosomes (13, 15, 18, 21, or 22), making answer (a) 1 extra chromosome correct.
Step-by-step explanation:
In humans, the appropriate number of chromosomes (euploid) is 22 pairs of autosomes and one pair of sex chromosomes. A discrepancy in this number results in aneuploidy, which includes loss (monosomy) or gain (trisomy) of chromosomes. Monosomy typically leads to non-viability of an embryo, demonstrating the critical nature of gene dosage. Most cases of autosomal trisomy are also lethal, yet trisomies of smaller chromosomes (13, 15, 18, 21, or 22) can lead to live births.
The survival of an individual with extra chromosomes depends on which chromosome is involved. Theoretically, a human could survive with one extra chromosome if it is one of the smaller chromosomes mentioned above. Thus, the most extra chromosomes a human could theoretically have without it being deadly is one, making the correct answer to the multiple-choice question (a). Down Syndrome is a condition involving trisomy 21, where the individual has 47 chromosomes due to an extra chromosome 21.
Tetraploidy, which would involve having 92 chromosomes in a cell, occurs when there is a duplication of all chromosomes, leading to an individual with double the normal diploid number. This condition is generally incompatible with life and would be exceedingly rare in live births.