Answer: Option I 

Easy Explanation by SamagraCS Team:

Definition: Basic COCOMO Model
The basic COCOMO model gives an approximate estimate of the project parameters.
The basic COCOMO estimation model is given by the following expressions:

Formula,
Effort = a∗(KLOC)b // Formula for Calculate Effort in person-months,
Tdev = c∗(Effort)d // Formula for Calculate Development time in month. 


Let’s Solve the Problem,  
 Given Parameters is:
project requiring one thousand source instructions.
Lines of code(LOC)=1000,
     We can write it KLOC = 1K,
 Multiplicative value 'a' = 3.6,
 Exponential value 'b' = 1.2.

Now put in the formula:

Basic COCOMO formula for Effort = a(KLOC)b 
                                = 3.6×(1)1.2 
                                = 3.6 x 1 
                                = 3.6 
Now Effort Value is = 3.6 Programmer Months.



So, Option(I)is correct.