(A) has something old (farm labor) being substituted for something new (machines). However, in (A), the cause of the substitution is that the old thing is becoming more expensive. In the stimulus, the cause of the substitution is that the new thing is more widely available. (A) would be more similar if it started with “because of the growing availability of farm machines...”.

The argument is talking about two versions of the same product that are substitutes for each other, and what happened to the old version when the new version became widely more available. (B) is talking about two different products.

(C) says that because a new option A entered the market, consumers reduced their consumption of the traditional option B. This is the same reasoning as in the argument.

(D) doesn’t have 2 things that are substitutes for each other. The child does less playing because he/she is forbidden from playing, not because he/she got a new option to watch movies instead of playing.

The argument talks about what happens to an old option (printed books) when a new option (audiobooks) becomes available: the new option is substituted for the old option. (E) doesn’t talk at all about whether one program is a substitute for the other, or whether one is newer.