Answer for exercise Grammar 1
The solution for exercise Grammar 1 in chapter 08 - Language focus 1 of Cutting Edge Upper-Intermediate - Student's Book by Sarah Cunningham, Peter Moor and Jonathan Bygrave
Question
Look at the website. Why is can correct in 1 but not 2?
Answer
Because in 2, there is already another modal verb, should. Only one modal verb can appear in a clause.