.c-txtsp{
  color: #000;
  font-size: 18px;
}
.tab_container {
  padding-bottom: 1em;
  background-color: #fff;
  border:1px solid #6fa8dc;
  margin: 0 auto;}
.tab_item {
  width: calc(100%/2);    /*100%/4を100%/2に変更*/
  padding:15px 0;
  border-bottom: 3px solid #6fa8dc ;
  background-color: #ececec;
  text-align: center;
  color: #6fa8dc ;
  display: block;
  float: left;
  text-align: center;
  font-weight: bold;
  transition: all 0.2s ease;
}
.tab_item:hover {
  opacity: 0.75;
}
input[name="tab_item"] {
  display: none;
}
.tab_content {
  display: none;
  padding: 1em 1em 0;
  clear: both;
  overflow: hidden;
}
#tab1:checked ~ #tab1_content,
#tab2:checked ~ #tab2_content {  /*, #tab3:checked ~ #tab3_content , #tab4:checked ~ #tab4_contentを削除*/
  display: block;
}
.tab_container input:checked + .tab_item {
  background-color: #6fa8dc ;
  color: #000;