Choice "B" is correct. Casualty losses are generally computed as the decline in fair market value, except that the fair market value is limited to the property's basis, here $150,000. Casualty losses are reduced by the amount of any insurance recovery, reducing this loss to $20,000. Next, each individual loss is reduced by $100, bringing this loss to $19,900. Finally, the remaining total amount of all casualty losses (here there is only one) are deductible only to the extent that the amount exceeds 10% of AGI, or $6,000 here. ($150,000 - $130,000$20,000; $20,000 - $100 - $6,000$13,900.)
Choice "a" is incorrect. This is the market value decline minus the adjusted basis.
Choice "d" is incorrect. This is the adjusted basis minus the insurance reimbursement, without any limitations being applied.
Choice "c" is incorrect. In addition to the $100 per loss nondeductible portion of each separate casualty loss, there is an overall limitation that the remaining total amount of all casualty losses is deductible only to the extent that it exceeds 10% of AGI.