The correct answer is C. 2.0.
The shape factor is a dimensionless quantity that is used to characterize the shape of a cross-section. It is defined as the ratio of the second moment of area of the cross-section to the product of the area of the cross-section and the square of the radius of gyration.
The second moment of area is a measure of the resistance of a cross-section to bending. The radius of gyration is a measure of the distribution of area around the centroid of the cross-section.
The shape factor is important in structural engineering because it is used to calculate the bending stress in a beam. The bending stress is the maximum stress that is developed in a beam when it is subjected to a bending load.
The shape factor for an isosceles triangle for bending about the axis parallel to the base is 2.0. This means that the resistance of an isosceles triangle to bending is twice as great as the resistance of a rectangle of the same area.
The other options are incorrect because they do not represent the correct value of the shape factor for an isosceles triangle for bending about the axis parallel to the base.