Many environmentalists, and some economists, say that free trade encourages industry to relocate to countries with ineffective or poorly enforced anti pollutions laws, mostly in the developing world, and
that, in order to maintain competitiveness, rich nations have joined this downward slide toward more lax attitudes about pollution.
(A) that, in order to maintain competitiveness, rich nations have joined this downward slide toward more lax attitudes about pollution - Correct
(B) that, for maintaining competitiveness, rich nations join in this downward slide toward more lax attitudes about pollution - 'for maintaining competitiveness' is bad idiomatic usage; 'rich nations join in this downward slide': fatal change in meaning. this wording implies that the rich nations are colluding with each other, metaphorically holding hands, deciding together to become more lax about pollution.
the simple present tense join implies that there is some sort of timeless truth about the statement being made. that's the wrong meaning: the sentence is meant to say that the rich nations have begun to do this as a result of current trends. if you don't understand the difference, consider the following analogous examples:
private universities have admitted more females than males --> meaning: this is an ongoing or cumulative trend, continuing into the present from some designated starting point
private universities admit more females than males --> meaning: this is a fundamental truth about the way private universities operate
(C) that rich nations join this downward slide toward more lax attitudes about pollution because of wanting to maintain competitiveness - same as B; because of verb-ing is unidiomatic
(D) that in rich nations, joining this downward slide toward more lax attitudes about pollution is a result of wanting to maintain competition - illogical meaning - it suggests that we are talking about some phenomenon that happens in rich nations, rather than talking about the actual actions of rich nations.
is a result of VERBing seems awkward
(E) that wanting to maintain competition is making rich nations join in this downward slide toward an attitude about pollution that is more lax - Tense issue
Answer A