1.Countries such as Brazil and Canada are large.
2.Countries, such as Brazil and Canada, are large.
3.Such countries, as Brazil and Canada, are large.
4.Such countries as Brazil and Canada are large.
a.I think only (2) is incorrect. Is it right?
b.Can I remove such as Brazil and Canada in (2) and as Brazil and Canada in (3)?Please tell me the rule?
c.What is the difference in meaning btw (1),(3) and (4)?Are they the same meaning?
You cannot remove such as Brazil and Canada in (2) without significantly changing the meaning. “Countries are large.” suggests that all countries are large.
Because of the word such, this sentence would (have to) refer back to a previous sentence about certain countries. Therefore it does not mean all countries. The main difference is that the additional information (Brazil and Canada) is missing.