You can find out word meanings by a s (one or more words that mean the same or almost the same as the unknown words)or an a in reading. eg. Cellphones have become ubiquitous ; you can see and hear them everywhere . The synonym "everywhere" tells you the meaing of "ubiquitous"(无所不有的) eg. Jane was talking with others while Eliza remained reticent all the time. According to the context clue, the meaning of "recticent" (沉默的,有保留的)is the opposite of "talking with others".