John sat down in his seat just in time; the class bell had just rung.
Explanation:
The first three have a transitional word, (but, whereas, although). So, they do require a semicolon. The last option has two independent phrases seperated by a semicolon. It is therefore, the correct option.
Ruri's mom taught her daughter in the end that she dosen't need anything to remember her friend by because she will always be in her heart just like her father is always in her heart. <span />