a) According to Benjy’s wife, there were swimmers who could swim faster than Benjy. If that happened, Benjy would come last in the race. There is an internal rhyme in this line: fast – last. There is humour in the expression which makes the reader laugh.
b) Benjy swam so slowly that a crab saw his toe. The crab followed him with the intention of biting him. The two lines present a clear picture of Benjy and the crab before our eyes. Such word pictures are called imagery. There is humour and exaggeration also.
c) Here is another imagery – Benjy’s wife falling into the lake with a great splash. She was so shocked at the prospect of her husband winning the race, that she fell into the lake. This is a way of exaggerating her reaction.