Choose the correct signal transduction pathway.
- Hormone $\to$ 7 TM receptor $\to$ G protein $\to$ cAMP $\to$ PKA
- Hormone $\to$ G protein $\to$ 7 TM receptor $\to$ cAMP $\to$ PKA
- Hormone $\to$ 7 TM receptor $\to$ G protein $\to$ PKA $\to$ cAMP
- Hormone $\to$ 7 TM receptor $\to$ cAMP $\to$ G protein $\to$ PKA