Which cell does not have a nucleus

In the human body fibrinogen is necessary for sealing cuts and stopping the loss of blood. since fibrinogen is made of chains of amino acids it is an example of which type of organic molecule

What is the difference between how ionic and covalent bonds form

Ialready know the answers to these questions and they are on the attachment. but i just need to know why that answer is the correct one. plz asap! this is for a report that i need to email by 10!