It has been years ________ I returned home.
A、afterC
译文：我回家已经有好几年了。此题考查连词since的用法。since表示“从(过去某事)以来，以后或到现在”时，主句多用完成时态。又如：WherehaveyoubeensinceIlastsawyou?自从我上次见到你以后，你到哪去了?
Ittookafewsecondsforhereyesto________tothedarkness.
______ofmeaningisaprocessbywhichawordthatoriginallyhadaspecializedmeaninghasnowbecomegeneralized.
—Davidhasmadegreatprogressrecently.—_______，and_______.
Ithasbeenyears________Ireturnedhome.
Fromtheviewpointofwordformation,theword“smog”isa______.
