Read the following article and select the best answer. Article: One hundred and fifty years ago, the world's first underground railway began operating in London, running for just six kilometres from Paddington to Famngdon.Today, the network covers 408 kilometres, with 11 lines running through 270 stations.And despite every major city in the world now having its own metro system, London's is still the second-longest (Shanghai's is the first).It's no surprise that locals and travellers will all be wishing London's "Tube" a very happy 150th birthday. Londoners have an unspoken code of conduct when they travel on me Tube, and a bit of local knowledge is essential for getting around the British capital.Here we provide some tips and etiquette for your next visit to London. Do... Stand on the right on escalators , walk on the left -Londoners will be quick at reminding you should you forget this. Let other passengers off before getting on. Give up your seat if someone needs it more than you. Mind the gap (between the train and the platform edge) -they are sometimes pretty wide. Don't... Block doorways-move down inside the carriages. Talk to people you don't know.Even if the train is delayed you should merely sigh or shake your head, rather than strike up a conversation. Travel on the Hammersmith & City or Circle lines if you can help it-they have a poor record for delays and disruptions. Expect air-conditioning-the low tunnels mean there's no space on most lines to install air-con equipment so expect to set hot and sweaty in summer. Question: What is the author's purpose in writing this text? - To wish the London Underground a happy birthday. - To provide tips for traveling by underground in London. - To explain the operation of the London Underground. - To inform passengers of the inconveniences on the Underground
Answer:
To provide tips for traveling by underground in London.