A.indoor air pollution can often make people seriously ill |
B.there may be more harmful gases outside the buildings |
C.man-made building materials give off dangerous gases |
D.the air indoors is polluted, which is very harmful |
A.every old house | B.every modern house |
C.all kinds of houses | D.all kinds of offices |
A.the man-made building materials and the limit of air-flow |
B.the building way that the builders want to save energy |
C.the building things that are made of man-made materials |
D.the limit of the flow of air between inside and outside |
A.plants can let out all kinds of pollutants indoors |
B.plants may take in more oxygen which people need |
C.plants can make our houses prettier and more healthy |
D.plants can absorb all kinds of harmful indoor chemicals |