1. How did dark matter affect the development of structures in the early universe? It seeded the development of galaxies.
It seeded the development of quasare
It cooled pockets of gas to form nebulae.
it became part of black holes

gold i'm pretty sure i might be wrong

the cover letter for a job search includes the skills one has for the particular job. including a cover letter is always a good idea, as it describes the ability to perform a task, and the employer can easily fetch the intention of the job you want to do.  

the cover letter is very important to be included in the job search document. hence, i strongly with the statement.