.kvImg-ab-test-alt {
  width: 100%;
  padding-top: 51.97917%;
  background: url("../images/kv_alt_pc.png") center center no-repeat;
  background-size: cover;
}

@media screen and (max-width: 639px) {
  .kvImg-ab-test-alt {
    padding-top: 178.66667%;
    background: url("../images/kv_alt_sp.png") center center no-repeat;
    background-size: cover;
  }
}