The diagram presents the electronic configuration of a particle that has a nucleon number of 40. The table lists the ideas proposed by three students, 1, 2 and 3, for identifying the particle. Student 1: Ar; Student 2: Cl; Student 3: $\mathrm{Ca}^{2+}$. Which of the students are correct?
- A1, 2 and 3
- B1 and 2 only
- C1 and 3 only
- D2 and 3 only