There are 10 points in a plane and 4 of them are collinear. The number of straight lines joining any two of them is `4` b. `40` c. `38` d. 39

Explanation

To solve the problem of finding the number of straight lines that can be formed by 10 points in a plane where 4 of them are collinear, we can follow these steps:

### Step 1: Calculate the total number of lines from 10 points
To find the number of straight lines that can be formed by any two points, we use the combination formula \( nC2 \), where \( n \) is the total number of points.

Here, \( n = 10 \):
\[
\text{Total lines} = \binom{10}{2} = \frac{10 \times 9}{2} = 45
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