Multi-select problem: How does the next paragraph end?

How to make soubise sauce
Melt 2 tablespoons (30 ml) of butter in a medium saucepan.
Add 2 tablespoons (30 gm) of flour to the butter to form a roux.
This is the first stage of any french sauce.

[a]. If the roux is not melted enough in this step, add more butter. Add 1/4 cup (30 ml) of vegetable oil to the roux.;
[b]. Instead of pre-cooking, however, you will use the shortening instead of the butter. The roux should be about 1/2 teaspoon ( g).;
[c]. Always keep the ratio of butter to flour equal when making a roux. If you're making the sauce thicker, use 3 tablespoons (45 ml) of each.;
[d]. It can be made by melting 1/3 cup (120 ml) of butter in a small saucepan to form a roux. The roux should be a reddish color.;
[c].