Many strange new means of transport have been developed in our century, the strangest of _______ being perhaps the hovercraft(气垫船).

The possibility __________ pleasant smells might reduce pain has recently been suggested by new research.

 _____________ on the portrait, mother was deep in thought.

 With the second ring road overpass _______ at present in Chengdu, the local citizens have to     choose another way to avoid traffic jam.

With the plane ________，some passengers on board feel sick and want to throw up.