题目5单选题
发送 AJAX POST 请求时,需设置的核心请求头是A. xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded", "POST")B. xhr.setRequestHeader("Content-Type", "form-data")C. xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded")D. xhr.setRequestHeader("Content-Type") = "application/x-www-form-urlencoded"