Thanks for the reply and for linking the other person's post, Campbell Ritchie.
Regarding answer C, what trips me up are not so much the rules regarding Lambda's and their various allowed syntaxes. Nor does the fact that answer C is correct surprise me. That much is quite clear to me.
Rather, what trips me up is the explanation of why answer C is correct.
Specifically, the explanation for answer C states that "Lambda expressions with one parameter are allowed to omit the parentheses around the parameter list, making option C correct".
Sure, it is merely stated that parentheses are allowed to be omitted, and so you can infer that they may either be present or absent. In that sense, the explanation of this rule regarding lambda's contains no mistake.
But the fact that it is allowed to omit parentheses most certainly does not make option C correct. In fact, the fact that parentheses are allowed to be omitted has no relationship to the correctness of answer C at all, since in answer C the parentheses are not omitted.
Phrased differently, the stated rule is that parentheses may be omitted. The argument is that this rule makes option C correct.
But if this rule did not exist, option C would still be correct since it does not omit the parentheses.
How, then, can we argue that this rule is what makes option C correct?
This is the error that I attempted to point out.
As for answer F, it uses the following syntax
Similar to answer C, the explanation states that "the return statement is optional when a single statement is in the body, making option F correct."
I suppose that technically, if the single statement is surrounded by brackets, then the return statement must be used. And if the brackets are omitted, then a return statement may not be used. So in that sense, one could argue that the return statement is somewhat optional.
But even if we apply such a lenient interpretation to the explanation, to state that answer F is correct specifically because the return statement is optional, when in fact the return statement is not optional for F due to the braces, strikes me as a mistake.
Ironically, the text then explains that for answer B, which was , that it is incorrect because a return statement must be used when braces surround the body.
The fact that the answer to B explains how the return statement is not optional when braces are present makes the mistaken explanation for F stand out all the more prominently.
The explanation to F says that the return statement is optional. The explanation to B says that it is not for a reason that also applies to F.
I, at least, find it hard to imagine that the authors intended the explanations to C and F to be this way.