[单选题]履带走行机械与车辆木地板的摩擦系数( )橡胶轮胎与车辆木地板的摩擦系数。
A. 等于
B. 大于
C. 小于
D. 符合

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)
A. essential
B. important
C. possible
D. inevitable