The celebration of Earth Day began in California, San Francisco. The first Earth Day celebration was held (1) ______ March 21st, 1970, which was the first day of spring. Earth Day now (2) ______  all over the world, either on the first day of spring or on April 22nd. We need to (3) ______   Earth every day, not just on Earth Day. Earth Day is important because it reminds us to stop and look at the problems of our environment, and to evaluate what we can do to prevent those problems. The most (4) ______ problems affecting Earth are pollution and loss of resources. Pollution causes damage to air, soil, and water. This affects all life on Earth. Pollution is caused by industries and individuals.

1. A. at                        B. on                                       C. in                            D. of

2. A. is celebrating      B. are celebrating                    C. is celebrated           D. are celebrated

3. A. take after             B. take care of                         C. take care                 D. take up

4. A. serious                B. seriously                             C. seriousest                D. as serious as