According to the meaning of the question, four different colors of flowers are planted in four areas: A, B, C and D.

Then there are four options in area A, and the color of area B is different from that of area A, so there are three options, that is, three situations.

The color of area C is different from that of area A and area B, and there are two colors to choose from, that is, two situations.

The color of area D is different from that of area B and area C, and there are two colors to choose from, that is, two situations.

Then four regions * * * have 4×3×2×2=48 schemes;

If red flowers are planted in both areas A and D, there are three situations in area B and two situations in area C,

There are 3×2=6 schemes for planting safflower in area A and D,

Then the probability of planting safflower in both area A and area D is 648 =18;

So choose a.