choice a the comparison made in choice a is ok. the real problems with choice a:
- 'the ratio of 42 times' is redundant; it'd be good enough just to say '42 times'. note that the word 'ratio' is not redundant in choices c-d, since it's being used as a modifier to make a logical connection.
- it doesn't say 42 times what. not only is that unacceptably vague, but it also breaks parallelism.

choice b is badly worded: 'compares to 42 times in 1980' seems to say that, on forty-two different occasions in 1980, the ceo:blue-collar ratio reached 419:1. this is not what we are trying to say.
more generally, when speaking about ratios as is done here, you can't just write "42 times" by itself. it has to be 42 times something. sometimes you can use pronouns - the height of the sears tower is more than four times that of the statue of liberty - but you can't use empty space.

choice c exhibits proper usage of 'times' followed by their pay. it also uses the ratio, a correct identification of exactly what is being described.

the construction in choice e doesn't make sense.since that's obviously not the case here——the report points out a fact about these CEOs, not the identities of the CEOs themselves。