Question

--- What are you doing？

--- I'm writing a talk________computer．I'll give the talk tomorrow．

1. A.
   on
2. B.
   about
3. C.
   to
4. D.
   for

Answer 1

A
不能用for，on在此处表示专门性的“有关”，句意为“我在写一篇有关计算机的报告。”