20. 使用厚薄規檢查導條和十字頭導板在J, K, L, M位置的間隙，翻譯成英文為Checked the clearance between guide strips and crosshead guide at position J, K, L and M by means of________.，其空格為下列何者？ (A) micro meter (B) dial gauge (C) thickness gauge (D) depth gauge