The official TOEFL test usually refers to TPO, which is the abbreviation of TOEFL online practice. It is the official model test question produced by ETS. The TOEFL test, which is closest to reality, was originally charged by sets, but it was cracked after it arrived in China. There are roughly two kinds of TPO on the market now, one is model testing software, and the other is online model testing. Most of the TPO model test software is not proofread, with many errors, no topic analysis and notes.