Điền giới từ:
1. ... some people swimming is a pleasant but not very active thing, to be enjoyed on a sunny day ... the beach ... a picnic ... afterwards.
2. Many governments are concerned nowdays .... the problem ... pollution.
3. The weather's terrible ... the middle ... summer. It's winter.
4. There is a cavern ... France ... which a railway line passes.
1. With / on / on / in
2. with / of
3. in / of
4. in / at