Exercise 2.8
 

I am a little bit confused of these theoretical problems, i'll post my answer here. Any insights appreciated.

For part (a), my answer is sort of paraphrasing the problem itself. Because g is the average function, it is a linear combination.

For part (b), my answer is an empty hypothesis set.

For part (c), the answer is obviously no. otherwise either all the data is +1 or -1.