Read the sentence and choose grammatically correct variant

1. the grass
   [is always|are always|always are|always is]
   greener on the other side (someone else's is always better)
2. the biter
   [is sometimes|are sometimes|sometimes is|sometimes are]
   bit (everyone gets what they deserve)
3. [to be often|often to be|to often be|be to often]
   wrong, never in doubt (it is better to make a mistake than to regret)
4. it
   [never rain|never rains|rain never|rains never]
   but it pours (trouble does not come alone)
5. travellers
   [usually is|usually are|is usually|are usually]
   cosmopolitan people (travellers feel comfortable everywhere)