烧结空心砖抗压强度等级为MU10.0、MU7.5、MU5.0和（）

A:MU15 B:MU3.5 C:MU2.5 D:MU2

根据抗压强度强度将砖和砌块分为MU20、MU15、MU10和（）等强度等级。

A:MU35 B:MU30 C:MU25 D:MU7.5

烧结空心砖和空心砌块的抗压强度分为MU10.0、MU7.5（）等几种。

A:MU15 B:MU5.0 C:MU3.5 D:MU2.5

空心砖的强度等级分为MU5.0、（）、MU2.0三个等级。

A:MU4.5 B:MU4.0 C:MU3.5 D:MU3.0

粉煤灰混凝土小型空心砌块按砌块抗压强度分为MU5、MU7.5、MU10、MU15、（）等几个等级。

A:MU2.5 B:MU3.5 C:MU20 D:MU25

轻集料混凝土小型空心砌块强度等级分为五级：MU3.5、MU5.0、MU7.5、（）。

A:MU1.5 B:MU2.5 C:MU10.0 D:MU15.0

烧结普通砖根据抗压强度分类可以分为（）及MU10五个强度等级。

A:MU35 B:MU30 C:MU25 D:MU20 E:MU15

Saving a City’s Public Art Avoiding traffic jams in Los Angeles may be impossible, but the city’s colorful freeway murals（壁画）can brighten even the worst commute. Paintings that depict（描述）famous people and historical scenes cover office buildings and freeway walls all across the city. With a collection of more than 2,000 murals, Los Angeles is the unofficial mural capital of the world. But the combination of graffiti（涂鸦）, pollution, and hot sun has left many L.A. murals in terrible condition._____（46）In the past, experts say, little attention was given to caring for public art. Artists were even expected to maintain their own works, not an easy task with cars racing by along the freeway. _____（47）The work started in 2003. So far, 16 walls have been selected, and more may be added later. Until about 1960, public murals in Los Angeles were rare. But in the 1960s and 1970s, young L.A. artists began to study early 20th-century Mexican mural painting._____（48） The most famous mural in the city is Judith Baca’s "The Great Wall," a 13-foot-high（4-meter-high）painting that runs for half a mile (0.8 kilometer) in North Hollywood,_____（49）it took eight years to complete—400 underprivileged teenagers painted the designs—and is probably the longest mural in the world. One of the murals that will be restored now is Kent Twitchell’s "Seventh Street Altarpiece." which he painted for the Los Angeles Olympics in 1984._____ （50）Twitchell said, "It was meant as a kind of gateway through which the traveler to L.A. must drive. The open hands represent peace." Artists often call murals the people’s art. Along a busy freeway or hidden in a quiet neighborhood, murals can reach people who would never pay money to see fine art in a museum, "Murals give a voice to the silent majority," said one artist.

A:The city trying to stop the spread of graffiti, has painted over some of the murals complete. B:This striking work depicts two people facing each other on opposite sides of the freeway near downtown Los Angeles. C:Artists like murals because they like the work of Mexican artists. D:Now the city is beginning a huge project to restore the city’s murals. E:The mural represents the history of ethnic groups in California. F:Soon, their murals became a symbol of the city’s cultural expressions and a showcase for L.’s cultural diversity.