Directions: For each blank in the following passage there are four words or phrases marked A, B, C and D. Fill in each blank with the word or phrase that best fits the context.
Reading involves looking at illustrative symbols and expressing mentally the sounds and ideas they represent. Concepts of reading have changed 1 over the centuries. During the 1950’s and 1960’s especially, increased attention has been devoted to 2 the reading process. Although experts agree that reading 3 a complex organization of higher mental 4 , they disagree about the exact nature of the process. Some experts, who regard language primarily as a code using symbols to represent sounds, 5 reading as simply the decoding（解码）of symbols into the sounds they stand for.
