it does not contain subgraphs homeomorphic to K₅ and K_{3, 3.}

it does not contain subgraphs isomorphic to K₅ or K_{3, 3.}

it does not contain subgraphs isomorphic to K₅ and K_{3, 3.}

it does not contain subgraphs homeomorphic to K₅ or K_{3, 3.}

$$\left( {\left( {{\rm P} \Rightarrow Q} \right) \wedge \left( {Q \Rightarrow R} \right)} \right) \Rightarrow \left( {{\rm P} \Rightarrow R} \right).$$

$$\left( {{\rm P} \Rightarrow Q} \right) \Rightarrow \left( { \sim P \Rightarrow \sim Q} \right)$$

$$\left( {{\rm P}\, \wedge \,\left( { \sim {\rm P}\,\,V \sim Q} \right)} \right) \Rightarrow Q\left( { \sim {\rm P} \Rightarrow \sim Q} \right)$$

$$\left( {\left( {{\rm P} \Rightarrow R} \right) \vee \left( {Q \Rightarrow R} \right)} \right) \Rightarrow \left( {\left( {\left( {{\rm P} \vee Q} \right) \Rightarrow R} \right)} \right)$$

TRUE

FALSE