Level 1, 5.7 quiz: 一 か 月

One of the questions in the 5.7 quiz asks: "What is the correct reading in Hiragana of the following word in Japanese? 一 か 月". Since the correct answer is "いっかげつ", I the question probably meant to ask for 「一ヶ月」 rather than 「ーか月」, right?

They should probably replace that question as it appears it's from lesson 5.13.   If you're doing the lessons in numerical order, you're being quizzed on something you haven't learned yet. 
 

Hmm. I seem to remember encountering ヶ月 earlier, but I can only find counters for minutes, hours and things down in module 2 right now. Maybe I'm mixing up my learning tools... >.

It's mentioned in the dialogue in lesson 1.4:

いっか げつ べんきょう して います。
一ヶ月勉強しています。
I have been studying for a month.

I don't think beginners take notice of that kanji and retain it all the way to lesson 5.7. 

The symbol is actually a katakana but it is not being used as katakana it is being used as a counter symbol for counting months.

If you were writing it in hiragana only it would be いっかげつ

If you were writing it in kanji then it would change to 一ヶ月

ケヶ notice the size difference. It is a smaller ke than the regular katakana symbol.

I haven't taken much notice of ヶ until now, and a quick search turned up an interesting Wikipedia page.
https://en.wikipedia.org/wiki/Small_ke

The page goes into fascinating detail about ヶ,  but here's a small sample:

The small ke is a Japanese character, typographically a small form of the katakana character ケ ke. While identical in shape to a small ケ, ヶ is actually an abbreviation for the kanji 箇, specifically by writing half of the bamboo radical 竹. 箇, alternatively written as 個, is a common Japanese counter word.