Title: Incandescent light bulb.
Question: When did Electro-Dynamic Light Company install its first lights?

Title: Immaculate Conception.
Question: What word substitution did he use in the authorization to appease all of the worshipers and view points when speaking of the inception of Mary  ?

Title: Catalan language.
Question: How many  reduced unstressed are vowels are there in Central Catalan?

Title: Time.
Question:
Which engineers came up with the first mechanical clocks?