What is the polynomial $3 y^2+(y+7)^2-15$ after it has been fully simplified and written in standard form?
A$4 y^2+34$
B$3 y^2+y+34$
C$4 y^2+14 y+34$
D$4 y^4+34$
A$4 y^2+34$
B$3 y^2+y+34$
C$4 y^2+14 y+34$
D$4 y^4+34$