Hello. 1. population aging 2. replaced 3. counterproductive 4. policy... has shifted the emphasis ... You need to use a noun form; population aging is like global warming -- not warming globe. This is subtle, but I prefer replace. Displace has a slightly more emotive connotation and that is inaccurate in this anodyne technical context. Also, we usually like the phrase "displaced by" and to know who or what is responsible for the displacement. Replace is neutral and matches the passive voice. Finally, displacement is used in an ongoing sense whereas replaced is usually used to present finality. This is simply counterproductive. Anything can be counterproductive -- not achieving its intended purpose at a minimum. However, counteractive is not used very often by itself; rather, it is used in the verb form "to counteract." It is usually used in contradistinction to the circumstances it is counteracting against. When preface with "proving to be", we need clarity -- not ambiguity. Effective or ineffective. Productive or counterproductive. This could go either way... if you remove "been", then it makes sense. If you remove "has been", it also makes sense. However, this pushes the verb tense further into the past and the statement adopts a matter of fact tone instead of a descriptive tone.

1. Population aging (careful on the spelling) 2. Replaced 3. Counterproductive 4. The government’s economic policy has shifted the emphasis from heavy industry to light industry.

Thank you Jane, that's very clear to me.

1. Population ageing has emerged in many developing countries as well ….. (as well as what? The meaning is a little unclear here). or The ageing population has emerged ..… (notice the use of the article 'the' … 'The ageing population). I prefer: Population ageing has emerged as a major challenge in many developing countries. 2. Coal has already been largely replaced as a fuel for electricity. Coal has largely replaced fuel for electrical generation (the sentence is a little awkward, so delete already, it doesn't add anything to the meaning and 'for electricity' doesn't read well. You could also say .…. for generating electricity 3. The continuous use of chemicals for the control of pests is proving to be counterproductive. 4. The government’s economic policy has shifted the emphasis from the heavy industry to the light industry. Or The government's economic policy has been shifted from emphasizing heavy industry to light industry. Or Government economic policy has shifted from heavy to light industry. This last sentence has is the best in my opinion, short, sharp and succinct. This makes for more stylish, academic writing. Which is what you want, right?