Final answer:
The correct answer is B. 'take out'. This phrasal verb is commonly used to express the act of obtaining or purchasing a service, which is suggested in the sentence.
Step-by-step explanation:
In the sentence, 'If you want to be sure of receiving a copy of the magazine, I suggest you ________ an annual subscription.' the best option would be B. 'take out'. This is because the phrasal verb 'take out' is commonly used to express the act of obtaining or purchasing a service such as an insurance policy, a loan, or in this case, a magazine subscription. The other terms mentioned - 'put down', 'write off', and 'send up', do not fit well in this context.
'Put down' can mean to write something, 'write off' means to cancel or dismiss something, and 'send up' means to make fun or parody something. None of these convey the act of obtaining a service, which is the action suggested in the sentence.
Learn more about Phrasal Verbs