Who does the leader of the Opposition designate as senior opposition MPs?

Okay, let's break down the role of Shadow Ministers in the UK political system. Think of the UK government as a team, and the Opposition as the team trying to win the next election. The Leader of the Opposition is in charge of that challenging team. To effectively scrutinize and challenge the government's policies, the Leader of the Opposition appoints senior members of their party as "Shadow Ministers." Each Shadow Minister is assigned to 'shadow' a specific government minister. For example, there's a Shadow Home Secretary who focuses on holding the actual Home Secretary accountable. This system allows the Opposition to develop alternative policies and present themselves as a credible government-in-waiting. So, the Leader of the Opposition designates Shadow Ministers as senior opposition MPs to mirror and challenge the government's actions. The other options, like Home Secretary or Chancellor of the Exchequer, are actual government positions, not roles within the Opposition. Local Mayors, while important, operate at a local level and aren't directly appointed by the Leader of the Opposition in Parliament.
Visualize a 'shadow' government challenging the official one; 'shadow minister' is the title they possess.