<option> values showing as 0 in database - php

Question

I cannot upload to the database drop down menu variables, when the form is submitted the text area is blank. I am new to coding and all of the information I have found thus far has been unable to help me. The students first and last names are submitting fine I just now need to process their grades
These are the Subjects:
English<br>
<select name="Grade">
<option value="-">-</option>
<option value="A*">A*</option>
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
<option value="Fail">Fail</option>
</select><br>
Maths<br>
<select name="Grade2">
<option value="-">-</option>
<option value="A*">A*</option>
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
<option value="Fail">Fail</option>
</select><br>
Science<br>
<select name="Grade3">
<option value="-">-</option>
<option value="A*">A*</option>
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
<option value="Fail">Fail</option>
</select><br>
I need to upload them to here:
$DB_HOST = "localhost";
$DB_USERNAME = "admin";
$DB_PASSWORD = "chichester";
$DB_NAME = "results";
$fname = $_POST["fname"];
$lname = $_POST["lname"];
$examboard = $_POST["examboard"];
$grade = $_POST["grade"];
$grade2 = $_POST["grade2"];
$grade3 = $_POST["grade3"];
$additionalcomments = $_POST["Additional Comments"];
$conn = new mysqli($DB_HOST, $DB_USERNAME, $DB_PASSWORD, $DB_NAME);
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = "INSERT INTO studentresults (Name,lastname,examboard,additionalcomments) VALUES ('$fname','$lname','$examboard','$grade','$grade2','$grade3','$additionalcomments')";
$sql = "INSERT INTO studentresults (grade, grade2, grade3) VALUES ('$grade','$grade2','$grade3')";
if ($conn->query($sql) === TRUE) {
echo "Student exam results have been successfully submitted. ";
} else {
echo "Error, please try again later. : " . $sql . "<br>" . $conn->error;
}
//close connection
$conn->close();
Now how do I overcome this, the script and database does not show an errors. All I need to do is process a series of exam results and display this in a database. The tag seems to have confused matters.

Answer 1

1) you are updating the insert query.
2) The query you have written is wrong as there number of columns is different than the number of values given.
3) $_POST["Additional Comments"]; this won't work, as array key cannot contain space.

Answer 2

Why do you have two $sql insert statements? Only use one.
INSERT INTO ___ (col1,col2) VALUES ('data1','data2');
You can't have spaces in $_POST['']; variables.