Nhận biết (M1)

Upper-atmospheric jets—phenomena whereby electrical discharges cause narrow cones of blue light to briefly burst upward from the tops of thunderclouds—have been observed reaching the ionosphere. The extreme altitudes involved (the ionosphere begins about 80 km above Earth) mark these gigantic jets as outliers; __________ the majority of jets reach heights of only 20 to 50 km.

Which choice completes the text with the most logical transition?

• A.

  consequently,

• B.

  indeed,

• C.

  in addition,

• D.

  nevertheless,