"It rained this morning."
"wa" is more like an indication of being. In English we would say "it" rained, not "is" rained. In Japanese there's often no need to specify the subject, so it's literally just "this morning rain fell"
That is wrong on so many levels. は/wa is a topic marker. です is equivalent to is/am/are/etc. And this sentence has a subject; it's 雨/rain, hence the subject marker, が, following it.
But you're right about one thing: the sentence translates literally to "this morning, rain fell." I think は would especially be used if you were contrasting this morning with, say, yesterday morning, in which it didn't rain.
no, wa is grammatically correct to use in this sentence. not using it is also correct. using wa marker means you introduce this morning as a topic of the conversation. you can ommit wa marker and neglect this morning as an important part of your conversation.
Yes, that should be correct, if it doesn't accept it you can click the report flag and they will hopefully fix it
It is from the verb "to fall" (ふる/降る) as in precipitation (rainfall, snowfall). So - Rain ((雨) が) fell (ふりました)! Or "Rained"!
They need to add the ability to put a comma in the answer to avoid confusion.