The binary subtraction 1110101 - 0011110 can be performed by borrowing from the next higher bit whenever necessary, similar to decimal subtraction. Let's break down the subtraction step by step:

Step 1: Borrowing
- In the rightmost bit, 0 cannot be subtracted from 1, so we borrow from the next higher bit.
- By borrowing a 1 from the next higher bit, we convert the leftmost bit of the second number (0011110) to 10.
- The new numbers become 1110101 - 0011110 = 1110101 - 1001110.

Step 2: Subtraction
- In the rightmost bit, 1 can be subtracted from 0, but with the borrowed 1, it becomes 10 - 1 = 1.
- In the next bit, 1 can be subtracted from 1, so it becomes 1 - 1 = 0.
- In the next bit, 1 can be subtracted from 1, so it becomes 1 - 1 = 0.
- In the next bit, 0 can be subtracted from 1, so it becomes 1 - 0 = 1.
- In the next bit, 1 can be subtracted from 1, so it becomes 1 - 1 = 0.
- In the next bit, 0 can be subtracted from 0, so it remains 0.
- In the leftmost bit, 1 can be subtracted from 1, so it becomes 1 - 1 = 0.

Step 3: Result
The result of the subtraction is 1010001.

Therefore, the correct answer is:
b. 1010001