Read the following statements and find out the incorrect statements.
a. A synapse is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron, which may or may not be separated by a gap called synaptic cleft.
b. At electrical synapses, the membranes of pre-and post-synaptic neurons are in very close proximity.
c. Electrical current can flow directly from one neuron into the other across chemical synapses.
d. Impulse trasmission across a chemical synapse is always faster than that across a electric synapse.
e. Electrical synapses are rare in our system.

Options

A. a and b
B. b and c
C. c and d
D. d and e

Explanation

To determine the incorrect statements from the given options, let's analyze each statement one by one.

### Step 1: Analyze Statement A
- **Statement A**: "A synapse is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron, which may or may not be separated by a gap called synaptic cleft."
- **Analysis**: This statement is correct. A synapse indeed consists of the membranes of the pre-synaptic and post-synaptic neurons, and they are typically separated by a synaptic cleft.

### Step 2: Analyze Statement B
- **Statement B**: "At electrical synapses, the membranes of pre-and post-synaptic neurons are in very close proximity."
- **Analysis**: This statement is also correct. In electrical synapses, the membranes of the neurons are very close together, allowing for direct electrical communication.

### Step 3: Analyze Statement C
- **Statement C**: "Electrical current can flow directly from one neuron into the other across chemical synapses."
- **Analysis**: This statement is incorrect. Electrical current flows directly between neurons at electrical synapses, not chemical synapses. Chemical synapses rely on neurotransmitter release.

### Step 4: Analyze Statement D
- **Statement D**: "Impulse transmission across a chemical synapse is always faster than that across an electrical synapse."
- **Analysis**: This statement is incorrect. Impulse transmission is faster across electrical synapses than chemical synapses due to the direct electrical connection.

### Step 5: Analyze Statement E
- **Statement E**: "Electrical synapses are rare in our system."
- **Analysis**: This statement is correct. Electrical synapses are less common compared to chemical synapses, which are more prevalent in the nervous system.

### Conclusion
The incorrect statements are:
- **C**: "Electrical current can flow directly from one neuron into the other across chemical synapses."
- **D**: "Impulse transmission across a chemical synapse is always faster than that across an electrical synapse."

### Final Answer
The incorrect statements are **C and D**.

---