Final answer:
To find the result of the given monomials, combine like terms and rearrange in decreasing order of powers of a, the result is -4a² - 5b².
Step-by-step explanation:
To find the result of the given monomials, we need to combine like terms. First, let's combine the terms with the same powers of a.
a³ - 5ab² - 6a²b² - 2a = a³ - 6a²b² - 5ab² - 2a = a³ - 6a²b² - 2a - 5ab²
Now, rearrange the terms in decreasing order of powers of a.
a³ - 6a²b² - 2a - 5ab² = a³ - 6a²b² - 5ab² - 2a
Therefore, the correct answer is d) -4a² - 5b².