bold specific word in email body while sending it

I am using a google spreadsheet which looks like:

   A             B                    C             D
1 Name        e-mail              Identifer       Status
2 Alex       ax@gmail.com         ERT ER          A
3 Micke      miike477@gmail.com   Ejyu er w       
4 John       john7788@tri.com     Arb Ed          C

I have a drop down list in column D (let say A,B & C for example), now i want that whenever the value changes (Initially the column D would be blank) in column D against a particular Name than an automatic e-mail trigger to e-mail id mentioned in column B by below mentioned sender id and content.

The email should be trigger whenever value changes in column D except for the blank, and if there were previously value was "B" and now it change to "C" than mail should be trigger.

Sender-example@gmail.com
CC-test1@gmail.com,test2@gmail.com

E-mail Body:

Hi Alex (Should be picked from column A depending against which name e-mail trigger)

some sentence here. some sentence here with your ERT ER (Should be pick from column C) has status A (should be pick from column D).

Regards,
example
123456789

I am trying using below mentioned script (which is working fine just want to bold value of identifier and status in e-mail body):

    function sendEmailToUser(event){
  var eventRange = event.range;
  var sheet = eventRange.getSheet();
  var sheetName = sheet.getName();
  var column = eventRange.getColumn();
  if (sheetName == "Sheet1" && column == 4){ // Make sure the edited column is in the correct sheet, otherwise editing Column D in Sheet3 might trigger this
    var row = eventRange.getRow(); // You need to know which row so you can send the email to the correct person
    var rowValues = sheet.getRange(row, 1, 1, 4).getValues();
    var name = rowValues[0][0];
    var sendTo = rowValues[0][1];
    var identifier = rowValues[0][2];
    var status = rowValues[0][3];
    if (status != "") { // Don't send the email if the status is blank
      var cc = "test1@example.com, test2@example.com";
      var subject = "What is the: " + identifier;
      var content = "Hi " + name + "\nWhat is the value " + identifier + " with the status " + status + "?";
      MailApp.sendEmail(sendTo, subject, content, {
        cc: cc
      });
    }
  }
}

You're mixing up your single and double quotes and also not concatenating them correctly. Please review Javascript Strings.

To concatenate '<body> and "Hi", you need to include the + operator as they're two separate strings:

'<body>' + "Hi"

BUT, the concatenation of '<body>' and "Hi" is unnecessary when you can simply write it as

"<body>Hi"

This is what you should be doing:

var content = "Hi " + name + "\nWhat is the value " + identifier + " with the status " + status + "?";
var contentHTML = "<body><p>Hi " + name + "</p><br><p>What is the value <b>" + identifier + "</b> with the status <b>" + status + "</b>?</p></body>";
MailApp.sendEmail(sendTo, subject, content, {
  cc: cc,
  htmlBody: contentHTML
});

content Will display the plain-text (unformatted) text for those users whose email clients (or by personal preference) do not display HTML email. contentHTML is the same, but shows the HTML formatted content.