题目内容
They’re not playing baseball today ___________ the rain.
A.because | B.as | C.since | D.because of |
D
解析
Prevention is better than cure. This saying has never been more appropriate than with reference to vaccination (接种疫苗). There are two main types of vaccines—live vaccines and killed or inactivated vaccines. Live vaccines are vaccines that contain disease causing antigens which are altered in such a way that weakens them to the point that they're no longer able to cause the disease. Killed or inactivated vaccines contain microbes (细菌) that have already been treated by chemical means to prevent them from copying or causing diseases. This means that any kind of vaccine for children cannot produce diseases, but can only help the body in creating antibodies that prevent that particular disease.
For a vaccine to make it to the market, its safety has to be confirmed. So most vaccinations for children are generally quite safe and are essential to children's health.
Vaccination can create immunity to various childhood diseases through deliberate artificial stimulation of the body's defenses. Among children, vaccinations not only prevent diseases and disorders, but also protect the health of the community, especially of those who aren't immunized (使免疫). For example, infants that are less than a year old cannot be given a measles (麻疹疫苗) vaccine but can be infected by measles. This can be prevented if people suitable for vaccination do get themselves vaccinated.
However, no vaccination is hundred percent safe, and there're always certain risks involved in vaccinations for children. For example, general side effects like pain, redness, headaches, swelling or a small lump at the site of the injection are common. Sometimes allergic (过敏) reactions may happen as well.
Therefore, when choosing any vaccination, parents should make an informed decision by weighing all pros and cons of vaccination for children. After all, the side effects of vaccines for children are far less severe, when compared to the symptoms of the diseases they prevent!
Title | (76)________ for Children |
(77)________ of vaccines | ?Live vaccines contain disease causing antigens that can weaken them to the point that they're (78)________ to cause disease. |
?Killed vaccines contain microbes treated by chemical means to avoid copying or (79)________ disease. |
|
(80)________ | ?Vaccination helps the body in creating antibodies that prevent the disease. |
Advantages | ?It can not only create immunity to childhood disease but it can also be helpful in (81)________ the health of a (82)________. |
(83)________ effects | ?Pain, redness, headaches, swelling or a small lump after the (84)________ are common. |
?Allergic reactions may also happen. |
|
Conclusion | ?Parents should weigh the pros and cons of vaccination when they (85)________ it. |