Using the two-line juxtapositions shown in (i) and (ii), (a) in what way does the second line "follow" the first, and (b) in what ways are the two lines like and unlike metaphors?
(i) At the pond children are collecting frogspawn. The old lady is labeling jars of jam.
(ii) The chancellor's new television has arrived. The dustmen couldn't find its box.
A juxtaposition is a literary device used to develop contrasts and comparisons. Specifically, juxtaposition is defined as when we place "side by side" any "two or more ideas, places, characters and their actions, etc." in any work of fiction in order to create the comparison or contrast ("Juxtaposition"). One classic exampled of juxtaposition we are given can be seen in Charles Dickens' A Tale of Two Cities:
It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epic of incredulity, it was the season of Light, it was the season of Darkness.... (as cited in "Juxtaposition")
In Dickens's entire opening paragraph, he juxtaposes a string of two opposing words or ideas, such as "wisdom" and "foolishness," "belief" and "incredulity," "Light" and "Darkness," etc.
If we look at your example (i), we see clearly that this is juxtaposing the concept of frogspawn to jam. We know that frogspawn is fertilized frog eggs that can look a bit like a dark colored jelly--think of caviar. We also know that the children are collecting the frogspawn. Ask yourself, what are they collecting the frogspawn in? Well, usually, children will collect bugs and critters and all manner of things in jars; hence, we can deduce that the children are collecting the frogspawn in jars. In the next line, we are told that an "old lady is labeling jars of jam." But we already know that frogspawn looks a great deal like jam, even though they are very, very different concepts. Despite the fact that they look alike, since frogspawn in a jar is very different from jam in a jar, we see that these two sentences are juxtaposing frogspawn with jam. Hence, the concept of labeling jars of jam follows from the idea of collecting frogspawn because both would be in jars and both look very similar.
To be able to complete your assignment, it will also be necessary to know exactly what a metaphor is. A metaphor is a type of figurative language in which we describe something further by relating it to another thing. One example of a metaphor can be seen in the sentence, "Her love is a red, red rose." This line is not saying that her love is like a rose, which would make it a simile; instead, the line is saying that her love is something that it's not, a rose.
We actually can see the juxtaposition in example (i) as a metaphor if we remember that frogspawn looks a lot like jelly or jam. Hence, we can see how this juxtaposition resembles a metaphor if we remember that the children are probably collecting the frogspawn in jars and that frogspawn in a jar could be described by saying that it is a jar of jam.
You can figure out the answers to the questions concerning the second juxtaposition in much the same way, but in order see how the sentences are a juxtaposition and how the second follows from the first, you'll need to first look up the definition of a dustmen. Plus, to be able to figure out if these two sentences can act as a metaphor, you'll need to think about exactly what a box has to do with a brand new TV set and if a brand new TV can be described by being likened to a box.