(1) is not correct because if they were identical twins they would be the same sex. (2) is not a valid reason. (4) is not correct. Thus, (3) is the correct option. The answer also corresponds to option (1) and why it's incorrect. If they were identical twins, they would not be both a female and male...
Answer and Explanation
The normal microbiota that harbouring an R plasmid will transmit its R plasmid to the normal microbiota because the normal microbiota does not have R plasmid after transmission of R plasmid its increases the resistance capacity of normal microbiota. This is the significance of normal microbiota that harbours an R PLASMID.
The mechanism that explains the movement of sugars throughout a plant is called the pressure-flow hypothesis. The driving force for sugar movement is transpiration. The main component of phloem sap is glucose.