Answer:
The correct answer is option 3. "Ab and aB".
Step-by-step explanation:
Crossing over of two chromosomes, or chromosomal crossover, is the exchange of genetic material between two homologous chromosomes. This genetic process is responsible for the genetic variations that occurs during sexual reproduction. Usually crossing over occurrs between matching genetic sequences, therefore a diploid invidual with an AB allele that crosses over with an invidual with ab allele will exchange each allele in equal parts. The resulting chromosomes will be Ab and aB, one part per allele.