Which of the following is correct:
(a) Cells of all living organisms have a nucleus.
(b) Both animal and plant cells have a well defined cell wall.
(c) In prokaryotes, there are no membrane bound organelles.
(d) Cells are formed de novo from abiotic materials.

Explanation

To determine which of the given statements is correct, we will analyze each statement one by one.

### Step 1: Analyze Statement (a)
**Statement:** Cells of all living organisms have a nucleus.
**Analysis:** This statement is false. Prokaryotic cells, such as bacteria, do not have a nucleus. Instead, their genetic material is located in a region called the nucleoid. Therefore, not all living organisms have cells with a nucleus.

### Step 2: Analyze Statement (b)
**Statement:** Both animal and plant cells have a well-defined cell wall.
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