Answer:
1, 3, and 4
Step-by-step explanation:
According to the United States Constitution, the following is true about Senate elections:
1. Only one-third of the Senate is up for re-election at one time: this is by Class 1, section 3 of the Constitution
2. States do not elect both senators in the same year: hence each of the state senators falls under different classes, thereby their election year defers.
3. Each senator has a term of at least six years: this is true according to the United States Constitution.