Answer
symmetric with respect to the x-axis, the y-axis, and the origin.
Work Step by Step
Step 1. To test symmetry with respect to the x-axis, replace $(x,y)$ with $(x,-y)$ to get $(x)^2+4(-y)^2=16$ which is the same as the original equation, thus it is symmetric with respect to the x-axis.
Step 2. To test symmetry with respect to the y-axis, replace $(x,y)$ with $(-x,y)$ to get $(-x)^2+4(y)^2=16$ which is the same as the original equation, thus it is symmetric with respect to the y-axis.
Step 3. To test symmetry with respect to the origin, replace $(x,y)$ with $(-x,-y)$ to get $(-x)^2+4(-y)^2=16$ which is the same as the original equation, thus it is symmetric with respect to the origin.