Which of the following is true of incomplete penetrance?a) Incomplete penetrance refers to cases in which individuals developing a particular disease (e.g., cancer or Alzheimer's) lack the typical genotype for this disease.b) Environmental factors do not influence penetrance.c) Incomplete penetrance implies that some individuals will experience less severe forms of disease such as cancer or Alzheimer's.d) Gene interactions have been shown to result in incomplete penetrance in some cases.