"Straks zou het lente zijn" ... While I'm totally okay with it being "Straks is het lente" or "binnenkort is het lente" I can't imagine what "straks zou het lente zijn" would translate to if not "soon it will be spring"!
The word voorjaar is a part of one of the other (wrong) alternatives. Is this a synonym to lente? Words that we haven't yet learned that are synonyms to words that we have learned often seem to be a part of these alternatives... :)