A.1~2 B.3~5 C.6~12 D.13~20
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