有誰能救救我，續上一次vb程式問題(編號：8841)

'顯示隨機抽取題號'
str = "丙檢試題.題號=" & R(1) & "or"
錯誤出在"From 丙檢試題 WHERE 丙檢試題.題號=str"這段程式，它一直出現(參數太少，預期個數1)這問題。如何改呢???
For i = 1 To 19
　　 str = str & "丙檢試題.題號=" & R(i) & "or"
　 Next i
str = str & "丙檢試題.題號=" & R(20)
　SQL = "SELECT 丙檢試題.題號, 丙檢試題.題目, 丙檢試題.選項一, 丙檢試題.選項二, 丙檢試題.選項三, 丙檢試題.選項四, 丙檢試題.難易度"
　SQL = SQL & " From 丙檢試題 WHERE 丙檢試題.題號= str"
　Adodc1.RecordSource = SQL