Hi, everyone! I have recently been banging my head on the following sentence:

The first thing I must do when I get home is study English.

Now, this is one of those cases when I *know* that it is right (but maybe not-so-normative), but I can't really justify it to my student. In the end, I am, quite honestly, lost.

The problem is that I know that modal auxiliaries cannot be followed by infinitives (i.e. [u]*must to study English[/u]), but this seems to be something else. I also cannot say that "The first thing I must do when I get home" is a compound subject because then the meaning would be something like "Apple is study English." I don't know!

Hence, can someone answer the following questions:

1. Can someone please break this sentence up into parts of speech in order to demonstrate any compound subjects/objects, etc.?
2. Are there, in fact, two clauses in this sentence?
3. Is this a correct sentence?
4. Is this a normative sentence?

Thanks!