The solution for exercise Grammar 2 in chapter 07 - Language focus 1 of Cutting Edge Upper-Intermediate - Student's Book by Sarah Cunningham, Peter Moor and Jonathan Bygrave
Question
Read the sentences below and answer the questions.
Answer
the first one (If you cross out the relative clause, the remaining sentence is Those missed the party. which doesn't make sense.)
the second one (If you cross out the relative clause, the remaining sentence is Pedro missed the party. which still makes sense.)
non-defining relative clauses (Non-defining relative clauses need commas, dashes or other punctuation to act as parentheses, as they contain extra, non-essential information.)