Which of the Following Is an Archimedean Copula Over Two

Multiple Choice

Which of the following is an Archimedean copula over two distribution functions

A) $$C \left( F _ { 1 } , F _ { 2 } \right) = \ln \left\{ - \left[ \left( \ln \frac { 1 } { F _ { 1 } } \right) ^ { a } + \left( \ln \frac { 1 } { F _ { 2 } } \right) ^ { a } \right] ^ { 1 / a } \right\}$$
B) $$C \left( F _ { 1 } , F _ { 2 } \right) = \exp \left\{ - \left[ \left( \ln \frac { 1 } { F _ { 1 } } \right) ^ { a } + \left( \ln \frac { 1 } { F _ { 2 } } \right) ^ { a } \right] ^ { a } \right\}$$
C) $$C \left( F _ { 1 } , F _ { 2 } \right) = \exp \left\{ - \left[ \left( \ln \frac { 1 } { F _ { 1 } } \right) ^ { a } + \left( \ln \frac { 1 } { F _ { 2 } } \right) ^ { a } \right] ^ { 1 / a } \right\}$$
D) None of the above.