Final answer:
Karen should focus on paying all her bills on time as the best strategy to improve her credit score. This shows her reliability in handling credit, which is crucial for lenders. Managing credit utilization and paying off credit card balances quickly also contribute positively to her credit score.
Step-by-step explanation:
The best strategy Karen can use to improve her credit score in preparation for purchasing an apartment is D) Paying bills on time. This practice demonstrates to lenders that she is responsible and reliable when it comes to managing her credit. By ensuring that all bills and loan payments are made on schedule, she avoids late fees and the potential negative impact on her credit score. It is also essential to manage credit utilization, meaning Karen should avoid using too much of her available credit. Additionally, paying off any carried credit card balances as quickly as possible can save on interest and better her credit health. Starting with a credit card from her own bank or a store might be easier, but she should always be mindful of interest rates and strive to pay off the balance monthly to avoid excessive charges.