155. Deep dives are less dangerous if helium is substituted for nitrogen, because under these pressures helium does not exert a similar narcotic effect.
The word "exert" is closest in meaning to which of following?
156. As a scuba diver descends, the pressure of nitrogen in the lungs increases. Nitrogen then diffuses from the lungs to the blood, and from the blood to body tissues.
The word "diffuses" is closest in meaning to which of following?
157. During ascent from a depth of 10 meters, the volume of air in the lungs will double because the air pressure at the surface is only half of what it was at 10 meters. This change in volume may cause the lungs to distend and even rupture.
The word "rupture" is closest in meaning to which of following?
158. In the twentieth century, electron microscopes have provided direct views of viruses and minuscule surface structures. The word "minuscule" is closest in meaning to which of following?
159. Unlike conventional electron microscopy, x-ray microscopy enables specimens to be kept in air and in water, which means that biological samples can be studied under conditions similar to their natural state.
The word "enables" is closest in meaning to which of following?
160. Because of the wavelength of the x-rays used, soft x-ray microscopes will never match the highest resolution possible with electron microscopes. Rather, their special properties will make possible investigations that will complement those performed with light-and electron-based instruments.
The word "Rather" is closest in meaning to which of following?