There are several ways to model a compound. One type of model is shown. 4 C's are connected in a line by 3 black lines. The C on the left has 3 H's attached to it each by a black line. The next C has 1 H attached by a black line and 1 O attached by 2 black lines. The next C has 2 H's attached to it by 1 black line each. The last C has 2 H's attached to it by 1 black line each and 1 O attached by a single black line. That O has an H attached to it by 1 black line.
What is the chemical formula for the molecule represented by the model?

CHO
C4H9O2
C4H8O
C3H8O2