When translating a mathematical equation into a words, you may find it easier to move from the outermost processes to the inner ones. From the equation y + 2z, the outermost process is addition, so we expect to look for "the sum" of two terms. Next we move on to the terms. The first term is simply "y", while the other term is 2z (product of 2 and z).
From the choices, the answer is D.
