The function g(x) = x^2 is transformed to obtain function h:
h(x) = g(x) + 1,
how is the graph of h different from the graph of g?

A. the graph of h is the graph of g vertically shifted up 1 unit.
B. the graph of h is the graph of g vertically shifted down 1 unit.
C. the graph of h is the graph of g reflected across the x-axis.
D. the graph of h is the graph of g vertically stretched.