AMC 8 2018 Problem 19

In a sign pyramid a cell gets a "+" if the two cells below it have the same sign, and it gets a "-" if the two cells below it have different signs. The diagram below illustrates a sign pyramid with four levels. How many possible ways are there to fill the four cells in the bottom row to produce a "+" at the top of the pyramid?

$\textbf{(A) } 2 \textbf{(B) } 4 \textbf{(C) } 8 \textbf{(D) } 12 \textbf{(E) } 16$