This question focuses on interpreting percent change relative to a baseline. When it says people walked 27% fewer steps after lockdown, it means the average steps dropped by 27% compared with what they walked before lockdown. That exact figure matches the described effect, so it’s the best choice. For context, if the pre-lockdown average was 10,000 steps, the post-lockdown average would be 10,000 × (1 − 0.27) = 7,300 steps. The other options describe smaller decreases or no change, which do not reflect the reported 27% drop.

Using multiple LID types leverages different stormwater processes to improve overall performance. Each LID type excels at certain tasks—some promote infiltration and groundwater recharge, others detain and slowly release runoff, some filter pollutants, and others boost evapotranspiration. When you combine them, the system can handle a wider range of rainfall events, adapt to varying soil conditions, and provide redundancy if one element underperforms. The result is better control of peak flows, reduced runoff volume, and enhanced water quality compared to relying on a single practice. They don’t perform identically, and properly designed LID reduces flood risk rather than increasing it, since it spreads and slows runoff on-site using the existing rainfall and runoff, not multiple external water sources.

LID BMPs aim to manage stormwater close to where it falls by mimicking natural hydrology, which means keeping water on the site, letting it infiltrate, evapotranspire, or be treated before it leaves. The goal is to reduce both the amount of runoff (its quantity) and the pollutants it carries, so downstream flows are less flashy and cleaner. Techniques like rain gardens, bioswales, permeable pavement, green roofs, and rain barrels put water back into the ground or atmosphere rather than sending it straight to streams. This is why the best choice is to reduce runoff quantity and pollution. The other options don’t fit because increasing runoff harms systems, eliminating permits isn’t a BMP goal, and focusing only on nutrients ignores the broader pollution and flooding issues LID addresses.

Cities drive around two-thirds of global greenhouse gas emissions. This happens because urban areas concentrate energy use for buildings, heating and cooling, lighting, transport, and industrial activity, all of which consume large amounts of energy in a relatively small area. The high density of people and infrastructure means emissions per area tend to be high, and urban systems are the backbone of economic activity, which further concentrates energy demand. Because of how we measure emissions — production-based within city boundaries or consumption-based accounting that includes energy embedded in goods and services consumed by city residents — the number commonly cited sits around 66%, a reasonable and widely used approximation. It’s larger than half and smaller than three-quarters or more, and figures like 75% or 90% reflect different definitions or methods rather than a single standard.