table.centrar tr:nth-child(even) {
  background-color: #f2f2f2;
}
table.centrar th {
  background-color: #4CAF50;
  color: white;
}
table.centrar td:nth-child(-n+2) {
 white-space:pre
 }
.centrar {
  text-align: center;
  margin-left: auto;
  margin-right: auto;
}
.tabla_form {
  width: 70%;
  margin-left: auto;
  margin-right: auto;
}
@media (min-width: 769px) {
.tabla_form td:nth-child(even) {
  text-align: left;
}
.tabla_form td:nth-child(odd) {
  text-align: right;
}
}
@media (max-width: 768px) {
.tabla_form td {
  text-align: center;
}
}