【名词&注释】
牙周膜(periodontal ligament)、全口义齿(complete denture)、人工牙(artificial tooth)、磨光面外形(polished surface)、吸附力(adsorption force)
[单选题]X线片上牙周膜间隙为 ( )
A. 0.05~0.15mm B. 1.5~3.5mm C. 2.5~3.5mm D. 0.15~0.38mm E. 超过2mm