When the pH of kaolinite suspension is increased, the absolute number of variable charges ( ).
A. does not change
B. decreases
C. increase or decrease
D. increases
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Soil mineral is the main component of soil, and it accounts for ( ) of the total solid weight.
A. above 95%
B. above 80%
C. 85%
D. 75%
The average carbon content of humic substances is ( ).
A. 45％
B. 38%
C. 58％
D. 65％
Which of the following does not belong to transported parent material?
A. Slope deposits
B. Residual deposits
C. Alluvial deposits
D. Colluvial deposits
Which of the following is not base cations?
A. H+
B. NH4+
Ca2+
D. K+
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