Problem: For the commercial naming of a product, the frame rate is often dropped and is implied from context (e.g., a 1080i television set). A frame rate can also be specified without a resolution. For example, 24p means 24 progressive scan frames per second, and 50i means 25 interlaced frames per second.
What does 50i mean?
The answer is the following: 25 interlaced frames per second

Problem: Valerian's first religious edict singled out Christianity as a particularly self-interested and subversive foreign cult, outlawed its assemblies and urged Christians to sacrifice to Rome's traditional gods. His second edict acknowledged a Christian threat to the Imperial system – not yet at its heart but close to it, among Rome’s equites and Senators. Christian apologists interpreted his disgraceful capture and death as divine judgement. The next forty years were peaceful; the Christian church grew stronger and its literature and theology gained a higher social and intellectual profile, due in part to its own search for political toleration and theological coherence. Origen discussed theological issues with traditionalist elites in a common Neoplatonist frame of reference – he had written to Decius' predecessor Philip the Arab in similar vein – and Hippolytus recognised a “pagan” basis in Christian heresies. The Christian churches were disunited; Paul of Samosata, Bishop of Antioch was deposed by a synod of 268 for "dogmatic reasons – his doctrine on the human nature of Christ was rejected – and for his lifestyle, which reminded his brethren of the habits of the administrative elite". The reasons for his deposition were widely circulated among the churches. Meanwhile, Aurelian (270-75) appealed for harmony among his soldiers (concordia militum), stabilised the Empire and its borders and successfully established an official, Hellenic form of unitary cult to the Palmyrene Sol Invictus in Rome's Campus Martius.
What did Valerian's second edict call the Christians' presence in the empire?
The answer is the following: threat

Problem: During the summers at Nohant, particularly in the years 1839–43, Chopin found quiet, productive days during which he composed many works, including his Polonaise in A-flat major, Op. 53. Among the visitors to Nohant were Delacroix and the mezzo-soprano Pauline Viardot, whom Chopin had advised on piano technique and composition. Delacroix gives an account of staying at Nohant in a letter of 7 June 1842:
What did Chopin help Pauline Viardot with?
The answer is the following: piano technique and composition

Problem: Among the first to study Russian dialects was Lomonosov in the 18th century. In the 19th, Vladimir Dal compiled the first dictionary that included dialectal vocabulary. Detailed mapping of Russian dialects began at the turn of the 20th century. In modern times, the monumental Dialectological Atlas of the Russian Language (Диалектологический атлас русского языка [dʲɪɐˌlʲɛktəlɐˈɡʲitɕɪskʲɪj ˈatləs ˈruskəvə jɪzɨˈka]), was published in three folio volumes 1986–1989, after four decades of preparatory work.
Who made the first dialectal Russian dictionary?
The answer is the following:
Vladimir Dal