In a Venn diagram monitoring $18$ -year-old students attending online courses during lockdown, the square represents students learning Spanish, the triangle represents those learning music, and the circle represents those learning photography.
The region counts are given as follows:



* Only Spanish = $40$
* Only Music = $45$
* Only Photography = $35$
* Spanish & Music only = $22$
* Music & Photography only = $28$
* Spanish & Photography only = $25$
* All three courses = $50$

What approximately is the percentage of students who are learning one course only?

1. A
   $48\%$
2. B
   $49\%$
3. C
   $50\%$
4. D
   $51\%$