这是我的代码。我正在从支持中获取学生的数据，对其进行过滤。我无法为选择选项设置默认值，而且两者都setAssignedStudent不起作用，在控制台中，我得到undefined. 请让我知道如何解决这个问题。

//here is sample of students array
// let students- [  {name: "abc", email:"abc.com", mentor:"" },  
// {name: "abc", email:"abc.com", mentor:"cda" },  {name: "abc", email:"abc.com", //mentor:"" }]
useEffect(() => {
    const getStudents = async () => {
      try {
        const res = await fetch("http://localhost:3001/students");
        const data = await res.json();
        //console.log(data);
        //filtering students based on who doesn;t have mentor
        let filter = data.filter((e) => {
          return e.mentor === "";
        });
        if (filter.length > 0) setStudents(filter);
      } catch (err) {
        console.log(err);
      }
    };
    getStudents();
  }, []);
 const [assignedStudent, setAssignedStudent] = useState(students[1]);
 const handleChange = (e) => {
    setAssignedStudent(
      students.find((student) => student._id == e.target.value)
    );
    console.log(assignedStudent);
  };
 const handleSubmit = async (e) => {
    e.preventDefault();
 console.log(assignedStudent);
}

<form onSubmit={(e) => handleSubmit(e)}>
          <select onChange={handleChange} value={assignedStudent}>
            {students.map((student) => {
              return (
                <>
                  <option key={student._id} value={student.id}>
                    {student.name}
                  </option>
                </>
              );
            })}
          </select>
          <button type="submit">Submit </button>
</form>