Then the three boys did not want to go so she picked out the

Then the three boys did not want to go so she picked out the next three girls.And i do not know then it was,but i think it was probably at this moment that the birthday party of Myra Sayla became fashionable.
and之前的是过去时 但是and之后又变成了一般时 为什么?还有 and什么时候可以写在句号后面?