The cation exchange capacity is highest of

The cation exchange capacity is a measure of how many cations can be retained on soil particle surfaces. Negative charges on the surfaces of soil particles bind positively charged atoms or molecules (cations) but allow these to exchange with other positively charged particles in the surrounding soil water.
CEC of vermiculite is 150, kaolinite is 3 - 15, chlorite is 10 - 40 and for montmorillonite CEC is 60 - 100.