在下列哪项研究中，血清学调查是唯一可行的方法（）。 A.疾病监测与预测 B.疾病的三

跨国连锁采购主要指制造商通过多家公司的购买力量，避免传统的分散采购中存在的物料灰色价格和交易回扣等现象，将触角伸向国际市场并得到更有竞争力的采购合同。

王某与一房地产公司签订商品房预售合同，预购商品房一套，并向登记机关申请办理了预告登记。随后该房地产公司将王某选购的商品房以更高价格销售给不知情的张某，并与张某依法办理了房屋所有权证书。下列说法中正确的是：（）

A．王某不能取得该房屋的所有权，因为房地产公司已经与张某依法办理了房屋所有权

证书

B．王某不能取得该房屋的所有权，只能追究开发商的违约责任

C．王某可以取得该房屋的所有权，因为房屋进行了预告登记

D．房地产公司未经王某同意进行房屋出卖的行为，不发生所有权变动的效力

杠杆在生产、生活中有着广泛的应用，如图所示，下列工具中属于费力杠杆的是

A．①、②

B．②、③

C．①、③

D．①、④

As viewed from space, the Earth’’s distinguishing characteristics are its blue waters and white clouds. Enveloped by an ocean of air consisting of 78% nitrogen and 21% oxygen, the planet is the only one in our solar system known to harbor life. Circling the Sun at an average distance of 149 million km (93 million miles), the Earth is the third planet from the Sun and the fifth largest planet in the solar system. Its rapid spin and molten nickel-iron core give rise to an extensive magnetic field which, coupled with the atmosphere, shields us from nearly all of the harmful radiation coming from the Sun and other stars. Most meteors burn up in the Earth’’s atmosphere before they can strike the surface. The planet’’s active geological processes have left no evidence of the ancient pelting it almost certainly received soon after it was formed. The Earth has a single natural satellite — the Moon.

This selection leads one to believe that the Earth________.

A．never gets hit by meteors

B．always gets hit by meteors

C．was hit by meteors some time in the past

D．may be bombarded by meteors in the near future

（）是商周时期用分铸法工艺打造的精美青铜器典型代表。

A.莲鹤方壶

B.四羊方尊

C.镇海吼