Powered flight requires fuel. For birds, that fuel is food; and since demands thta bulk and weight should be (7)____ to a minimum, the more compact and powerful that fuel is, the (8)____. Seeds have both those qualities. The nourishment they contain is there to enable a developing seedling to build a stem and leaves so that it can start to manufacture food on its own (9)____, but that same nourishment can also feed birds and it is so rich and so conveniently packaged that many birds eat little else. (10)____ it is of no benefit to a plant to have its seeds destroyed in the stomaches of birds, many plants armour their seeds to prevent that (11)____. Birds, in response, have evolved special tools and strategies to ensure that they can continue to plunder this valuable food supple that (12)____ their needs so well.

7. A: kept    B: managed    C: maintained    D: controlled

8. A: greater   B: better   C: lighter   D: higher

9.A:accord    B: account    C: way    D: terms

10. A: Although   B: While    C: Despite   D: Since

11.A: happening  B: appearing   C: following   D: proceeding

12. becomes    B: agrees   C: suits    D: pleases