What is the main finding about carbon dioxide in Roger’s report?

In this section, you will hear five short news items. After each item, which will be read only once, there will be a twenty-second pause. During the pause, read the question and the four choices marked A, B, C and D, and decide which is the best answer. Then mark the corresponding letter on the answer sheet with a single line through the centre.
16. Carbon dioxide levels in the atmosphere have reached a symbolic high. For the first time in human history, daily measures of CO2, which is an important factor in global warming, have topped 400 parts per million. Roger Harrabin reports.
17. A woman is recovering in hospital after being rescued from the rubble of the garment factory that collapsed 17 days ago in Bangladesh. She’s said to have survived by drinking from a water pipe and scavenging for food in the lunch boxes of dead colleagues. Andrew North reports from Dhaka
18. The United Nations human rights chief Navi Pillay has expressed concern over a build-up of Syrian government troops around the rebel-held western town of Qusair. She said she feared the troop build-up was in preparation for a major attack on Qusair. The government is reported to have dropped leaflets over the town, warning the population to leave.
19. Morocco has officially started to work on the first phase of a massive solar energy complex on the edge of the Sahara Desert. It’s hoped the plant’s capacity will reach 500 megawatts by 2020. Together with four other plants gifted to be built at different sites, the combined solar capacity in Morocco should reach 2, 000 megawatts by that time.
20. Student loan debt is soaring. The American Institute of CPAs recently took a survey of student loan borrowers, and found the money they owe has made some of them postpone buying cars or houses, in some cases even delay getting married. What’s more, 60 percent of them said they have some regret about taking out student loans. So, what’s a student who’s planning on college to do?