Explain why most farmers use stem cuttings to plant new fruit trees rather than plant seeds.

The main reason that most farmers use stem cuttings rather than just planting a seed is that a tree's genetic variation will occur. The seeds of many fruit trees tend to vary differently from the parent, because seeds themselves are produced by sexual reproduction (i.e they receive genes from a male and female to form). As they are a cross from two sets of genes, many fruit trees are not “true to seed”. Their seeds will produce a generally different variety of tree from the parent. When using stem cuttings, it's almost like a cloning process.

cause the stem cuttings will spread like bulbs and its quicker.

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.