A.池底沒有腐草爛葉沉積,并為砂質(zhì)土壤 B.池底沒有腐草爛葉沉積,并為粘質(zhì)土壤 C.池底有豐富的腐草爛葉沉積,并為砂質(zhì)土壤 D.池底有豐富的腐草爛葉沉積,并為粘質(zhì)土壤
A.20 B.50 C.80 D.110
A.1 B.2 C.3 D.4