To prevent blood flowing back after each heartbeat. They ensure that the blood flows only in one direction (back to the heart).          
        
             
        
        
        
Translocation
hope this helps and maybe a brainly?
        
             
        
        
        
 
 
1. Sand particles are too big to dissolve so their density sinks them 
2. Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles.
 
        
             
        
        
        
The mRNA needs to copy the gene sequence of the dna before it leaves the nucleus to the tRNA and rRNA
        
             
        
        
        
1:I'm pretty sure the answer is Metaphase because the cell didn't split apart or start to yet.
2: Is Anaphase
3: Telophase
4: Cytokinesis