Final answer:
The ampacity of each 1/0 THHN conductor when there are four current-carrying conductors installed in a raceway in a dry location is 136A.
Step-by-step explanation:
The ampacity of each 1/0 THHN conductor when there are four current-carrying conductors installed in a raceway in a dry location is 136A (option B).
The National Electrical Code (NEC) provides tables that list the allowable ampacities for different types and sizes of wires. According to Table 310.15(B)(3)(a) of NEC, when there are four current-carrying conductors bundled together, the ampacity of each conductor is derated to 80% of the ampacity listed for a single conductor. The ampacity listed for a single 1/0 THHN conductor is 170A, and 80% of that is 136A.
Therefore, the correct answer is option B, 136A.