The correct answer is A. Imagine.
To conceive of something means to think of it or imagine it. In this case, the speaker is saying that they cannot imagine a time when they did not have a refrigerator. This means that they have always had a refrigerator in their life and they cannot picture what it would be like to live without one.
The other options are not correct because they do not accurately reflect the meaning of the sentence.
B. Give birth means to bring a child into the world. This is not what the speaker is saying. They are not saying that they cannot imagine giving birth to a refrigerator. They are saying that they cannot imagine a time when they did not have a refrigerator.
C. Understand means to know the meaning of something or to be able to explain it. This is not what the speaker is saying. They are not saying that they do not understand what a refrigerator is. They are saying that they cannot imagine a time when they did not have one.
D. Depend means to rely on something or someone. This is not what the speaker is saying. They are not saying that they rely
on their refrigerator. They are saying that they cannot imagine a time when they did not have one.