根据以下例子的划线部分，判断作者采用哪种方法指出当...

根据以下例子的划线部分，判断作者采用哪种方法指出当前研究的问题（Identify a problem）？ The findings of studies examining the use of various forms of computer-assisted instruction (CAI) have been mixed. Studies by Hickey (citation 5) and Honeycutt (citation 6) indicated superior results with CAI while studies by Ellis (citation 7), Caldwell (citation 8) and Belzer (citation 9) indicated little or no significant effect. Although much work has been done to date, more studies need to be conducted to ascertain the effects of microcomputer-assisted instruction in teaching various subjects in a variety of learning situations.

A、Indicating a gap

B、Raising a question

C、Disagreeing with the existing approach

D、Extending a finding