Most plants can make their own food from sunlight, (1) some have discovered that stealing is an easier way to live. Thousands of plant species get by (2) photosynthesizing, and over 400 of these species seem to live by pilfering sugars from an underground (3) of fungi(真菌). But in (4) a handful of these plants has this modus operandi been traced to a relatively obscure fungus. To find out how (5) are (6) , mycologist Martin Bidartondo of the University of California at Berkeley and his team looked in their roots. What they found were (7) of a common type of fungus, so (8) that it is found in nearly 70 percent of all plants. The presence of this common fungus in these plants not only (9) at how they survive, says Bidartondo, but also suggests that many ordinary plants might prosper from a little looting, too.

Plants have (10) relations to get what they need to survive. Normal, (11) plants can make their own carbohydrates through photosynthesis, but they still need minerals. Most plants have (12) a symbiotic relationship with a (13) network of what are called my corrhizal fungi, which lies beneath the forest (14) . The fungi help green plants absorb minerals through their roots, and (15) , the plants normally (16) the fungi with sugars, or carbon with a number of plants sharing the same fungal web, it was perhaps (17) that a few cheaters—dubbed epiparasites—would evolve to beat the system. (18) , these plants reversed the flow of carbon, (19) it into their roots from the fungi (20) releasing it as "payment.\

10（）

A.business

B.commercial

C.trading

D.exchanging

如图所示，蛛网膜下隙穿刺时，穿刺针穿过的组织层次为（）

A.皮肤、皮下组织、棘上韧带、棘间韧带、黄韧带、硬膜外腔、硬膜

B.皮肤、皮下组织、棘上韧带、硬膜外腔、黄韧带、硬膜下腔、硬膜

C.皮肤、皮下组织、黄韧带、棘上韧带、硬膜外腔、棘间韧带、硬膜

D.皮肤、皮下组织、棘上韧带和棘间韧带、硬膜外腔、黄韧带、硬膜

E.皮肤、皮下组织、棘间韧带、棘上韧带、硬膜、黄韧带、硬膜外腔