Substituting a2+b2 for z and ab for y into the expression 4z+8y give 4(a2+b2)+8ab. Multiplying a2+4b2+8ab,or eqivalently 4(a2+2ab+b2).Since (a2+2ab+b2)=(a+b)2 , it follows that 4z+8y is equivalent to (2a+2b)2. Choices A, C, and D are incorrect and likely result from errors made when substituting or factoring.