Note see my answer at https://judaism.stackexchange.com/questions/43708/if-a-virgin-birth-actually-disqualifies-a-messianic-candidate-how-then-should-i/71602#71602

Your question B answers question A. Thus `הָעַלְמָה` (the young woman) was married but *Rashi* say was not **yet** pregnant with her first child.

That is Rashi and Ibn Ezra point to this pasuk to show that even if she was not yet pregnant, she was married to Yeshaya. Radak says that it was the young wife of Achaz

Since the young woman was known to the king and was going to be involved in a *sign*, then she would not become pregnant while unmarried.


Those who translate the verse to mean *is currently pregnant* obviously state that the word `הָעַלְמָה`cannot **in this verse** mean unmarried. Additionally, they disagree with Rashi as to meaning that she will become pregnant.

> But according to the Hebrew and Aramaic Lexicon of the Old Testament,
> a leading scientific lexicon, an 'almah is 'a young woman (until the
> birth of a first child).'
> 
>  Please explain fully. If the lexicon is correct, then the
> speculations of Ibn Ezra and Rashi have no sound lexicographical
> basis.

Note that Rashi and Ibn Ezra are stating that this would be her **first** child and that he would be born **during the coming year**. Thus, they do fit with your lexicographical citation.

Ibn Ezra cites [Mishlei 30:19](http://www.chabad.org/library/bible_cdo/aid/16401#v=19&showrashi=true) to show that the word cannot be *virgin* as 

> the way of a man with a young woman.

is given as one of those things that cannot be detected (after a short time). If she was a virgin, one could tell that she is no longer a virgin.

This also shows that it can mean a married **or** unmarried woman.

[Isaiah 7:14](http://www.chabad.org/library/bible_cdo/aid/15938#v=14&showrashi=true)

> **is with child**: This is actually the future, as we find concerning Manoah’s wife, that the angel said to her (Judges 13:3): “And you
> shall conceive and bear a son,” and it is written, “Behold, you are
> with child and shall bear a son.”
> 
> **the young woman**: My wife will conceive this year. This was the fourth year of Ahaz.

This means that she was married, but had not yet conceived, but was about to in the near future.

Art Scroll Tanach translates it in accordance with Rashi (will become pregnant).