30.The problem of global warming ______ for decades.
A: has been existed
B: has existing
C: being existed
D: has existed
A: has been existed
B: has existing
C: being existed
D: has existed
举一反三
- There _____ to be nobody in the office. A: happened B: has C: existed D: is
- As a phenomenon, intercultural communication has existed for thousands of years.
- 2，Lao Jin' s winter swimming team has existed for ________ years. A: 30 B: 25 C: 20 D: 35
- Systematic education for real estate development has not truly existed until the last decade.
- The reason of global warming is the has been changed.