When the length of a simple pendulum is increased, the time period of oscillation changes. The time period of oscillation is the time taken for the pendulum to complete one full back-and-forth swing.

In a simple pendulum, the time period is directly proportional to the square root of the length of the pendulum. This means that as the length of the pendulum increases, the time period also increases.

In this question, we are told that the length of the pendulum is being increased by 4-fold. This means that the length is being multiplied by 4. According to the relationship between time period and length, when the length is multiplied by 4, the time period should increase by a factor of 2.

Therefore, the correct answer is option 4: the time period of oscillation will be increased by a factor of 2 of its initial value.