-   0.75 MP = 0.8 CP (since 20% loss) So, MP = 1.0666CP ⇒ 6.66% gain.

Given:
List Price (LP) = 100
Selling Price (SP) = 3/4 LP
Loss = 20%

We need to find the Profit Percentage (P%) if he sells at the List Price (100).

We can use the following formula to calculate the Profit Percentage (P%):

P% = (SP - CP)/CP × 100

where, SP is the Selling Price and CP is the Cost Price.

Since, the person incurs a loss of 20%, we can say that the Cost Price (CP) = (1.2 × SP).

Therefore, the Profit Percentage (P%) = (SP - 1.2 × SP)/(1.2 × SP) × 100

Substituting the values, we get

P% = (3/4 LP - 1.2 × 3/4 LP)/(1.2 × 3/4 LP) × 100

= (3/4 LP - 9/10 LP)/(9/10 LP) × 100

= (LP/40)/(9/10 LP) × 100

= 40/9 × 100

= 6.66 %

Hence, the Profit Percentage (P%) if he sells at the List Price (100) is 6.66 %.

Therefore, the correct answer is Option B 6.66 %.