Some regions of ocean rich in many nutrients contain very low concentrations 4 h" a1 \5 t# E
of iron, so relatively little plankton grows there. Adding small amounts of iron \, I3 P7 J* Z
to such areas of ocean soon produces a 30- to 40-fold increase in plankton.
0 [% k6 \$ A9 {+ ^% d- \( c& oIn such amounts plankton absorbs large quantities of carbon dioxide, a gas
1 \$ M' g; v6 q4 aimplicated in global warming. Therefore an effective way of reducing global
- a) _- p2 X) K/ m2 L7 Awarming would be to add iron to all such regions of ocean.
7 c/ Y* v0 o4 z, b# d+ f Which of the following, if true, provides the strongest evidence that the method - S k( a' p# A" L: V. P3 n0 K1 u2 J
outlined, if put into effect, would not reduce global warming?
5 w4 P' r# }, b5 }; v. ` A Many regions of ocean that lack iron, and thus plankton, contain most of
+ `' ]3 d+ k5 J* i2 l the same dissolved minerals as regions rich in both iron and plankton.
6 [1 }* w% X- n. v: M! u# n B Some regions of ocean that are already rich in iron are too poor in other 4 H3 v: k% B/ P- \# ~/ O
nutrients to support significant plankton populations.
* M# d+ V$ z* ^ C It would be very expensive to put into effect a program of adding iron to
6 Z1 {8 g# U7 B9 }4 }7 a all the nutrient-rich regions of ocean that lack iron. % R: v7 W% F4 @% R! k1 x1 ^
D Rapid surges in the amount of plankton in the ocean often lead to $ ~$ a) N2 U" ^8 y: N4 r# P
increased emissions of methane, a gas also implicated in global
7 f- n2 D" M( u. d* E/ x1 m warming. ' Z0 L9 G8 L# u6 M) `
E In regions of ocean where there are levels of nutrients sufficient to 2 `( r! R7 T8 I1 ^( f7 ?9 o% A
support large plankton populations, the size of the population varies
* A( f' X, Z5 i/ q7 l4 k- J with the season.
0 Y* G- c8 g( `! q答案:D |