か usage in subordinate clauses

Question

So I know there are many uses of か, but the one I want to focus on is using a question word with か. For example:

何を食べるか知ってる？

何を食べるか知っていますか？

For these two sentences, the か inbetween the two words acts as a connector and replaces the particle. However, I was wondering what to do if this か is at the end of a sentence. For reference, I am trying to write the following:

The contents of the reading are about how baseball entered Japan.
あの読み物の内容はどうやって野球が日本に入ったか。

What I am unsure of is how to end this sentence is both plain and polite ways, i.e.

あの読み物の内容はどうやって野球が日本に入ったか

or

あの読み物の内容はどうやって野球が日本に入ったかです

or something else.

Answer 1

An embedded question using か forms a noun. You can say 何を食べるかを知っていますか, although this を is usually omitted. Likewise, you can attach だ/です to an embedded question, too. People often insert a comma between か and だ/です.

この読み物の内容は、野球がどうやって日本に入ってきたか、です。
This article is about how baseball entered Japan.

これは野球がどうやって日本に入ってきたかについての読み物です。
This is an article about how baseball entered Japan.

大事なのは明日雨が降るかどうかだ。
What is important is whether or not it will rain tomorrow.

株価がどうなるかに注目しています。
I'm paying attention to what will happen to the stock price.