In a solenoid, the magnetic field inside the solenoid is directly proportional to the current flowing through the wire and the number of turns per unit length of the solenoid.

Option 1: B - This option suggests that the magnetic field will remain unchanged. However, as the number of turns per unit length is increasing, this option is unlikely to be correct.

Option 2: IB - This option suggests that the magnetic field will be multiplied by the current flowing through the wire. Since the current is represented by I, this option is correct.

Option 3: BI2 - This option suggests that the magnetic field will be multiplied by the square of the current flowing through the wire. However, the correct representation for this would be I^2, so this option is not correct.

Option 4: BiA - This option suggests that the magnetic field will be multiplied by the current and a variable A. Since the variable A is not mentioned in the question or explanation, this option is not meaningful.

Therefore, the correct answer is option 2: IB. Increasing the number of turns per unit length in a solenoid will increase the magnetic field inside the solenoid, and the new magnetic field value will be equal to the original magnetic field