Final answer:
The statement about equijoin being the most common type of join in database operations is true, and 'suggestion' is the term that is closest in meaning to hypothesis.
Step-by-step explanation:
The statement that the most common type of join is an equijoin, which joins two or more tables together based upon the tables having equivalent data values in a common column, is true. An equijoin is indeed widely used in SQL and other database-related operations to merge rows from two or more tables.
As for the second part of your question, the word that is closest to the same meaning as hypothesis would be d. suggestion. A hypothesis is essentially a tentative explanation or prediction that can be tested by further investigation.