they are of the environmental pollution a major factor 这句话错哪

The Royal Commission on Environmental Pollution has just published a report on new materials and has looked at the case of nanotechnology（纳米技术）, which describes the science of the very small. Nanotechnology covers those man-made materials or objects that are about a thousand times smaller than the microtechnology（微电子技术）we use, such as the silicon chips of computers.
Nanotechnology gets its name from the nanometer, which is a billionth of a meter. There are about 600 consumer products already on the market that use nanotechnology. Nanomedicine is also being developed to fight cancer and other fatal diseases.
The Royal Commission found no evidence of harm to health or the environment from nanomaterials, but this “absence of evidence” is not being taken as “evidence of absence”. In other words, just because there are no apparent problems, this is not to say that here is no risk now or in the future. The commission is concerned about the pace at which we are inventing and adopting new nanomaterials, which could result in future problems that we are ill-equipped to understand or even find with current testing methods.
One of the problems about nanotechnology is that when we make something very small out of a well known material, we may actually change the functionality of that material even if the chemical composition remains the same. Indeed, it is not the particle（颗粒）size that should concern us, but its functionality. Take gold, for example, which is a famously inert (惰性) substance, and valuable because of it. It doesn’t rust or corrode because it doesn’t interact with water or oxygen. However, a particle of gold that is between 2 and 5 nanometers in diameter becomes highly reactive. This is not due to a change in chemical composition, but because of a change in the physical size of the gold particles. How can a change in size result in a change of function? One reason is to do with surface area. Nanoparticles have relatively a much bigger surface area. It is like comparing the surface area of a basketball with the total surface area of many pea-sized balls with the same weight of the single basketball. The pea-sized balls have a surface area many hundreds, indeed thousands of times bigger than the basketball, and this allows them to interact more easily with the environment. It is this increased interactivity that changes their functionality—and makes them potentially more dangerous to health or the environment.
小题1:Why does the writer mention microtechnology in the first paragraph?

A．to introduce the topic of nanotechnology

B．to help us better understand nanotechnology

C．to help us know more about microtechnology

D．to compare microtechnology with nanotechnology

小题2:The example of the “gold” in the last paragraph is intended to show that_________.

A．gold is valuable because it is an inert substance

B．an inert substance like gold doesn’t interact with water or oxygen

C．the function of gold is steady because it is an inert substance

D．the function of gold changes when made into something very small

小题3:Which process explains that there might be risks in nanotechnology?

A．expand surface area →increase interactivity → change functionality→cause possible dangers

B．expand surface area → change functionality → increase interactivity →cause possible dangers

C．increase interactivity → expand surface area → change functionality→cause possible dangers

D．increase interactivity → change functionality → expand surface area→cause possible dangers

小题4:What does the passage mainly focus on?

A．the introduction of nanotechnology and its wide use

B．the present use of nanotechnology and its future

C．the potential danger nanotechnology may bring us

D．the proposal to stop nanotechnology due to the potential danger