The correct answer is:
D) a basic savings account.
Step-by-step explanation:
Liquidity means ability to withdraw your money quickly.
A savings bond takes time, often years, to mature.
A money market account is fairly liquid, although it can take up to 7 days to withdraw your money.
A certificate of deposit (CD) can be easily withdrawn, but you will lost interest if you do not fulfill the entire term of the CD.
With a basic savings account, you can withdraw money at any time; however you may experience fees for not having met the minimum balance requirements if you're not careful.