Challenge 1: Identify Client and Server — Possible Solution
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(a) Weather app on your phone showing today's forecast
    -> CLIENT: the weather app on your phone.
    -> SERVER: a remote weather data provider somewhere else, holding
       the actual forecast data.
    The app doesn't calculate the weather itself — it sends a request
    ("what's the forecast for this location?") to a server and
    displays whatever comes back.

(b) A browser loading a news website
    -> CLIENT: the browser.
    -> SERVER: the news website's web server.
    The browser asks for a page; the server sends back the HTML,
    images, and article content that make up that page.

(c) A smart thermostat reporting the current temperature to an app
    -> CLIENT: the thermostat.
    -> SERVER: whatever backend service the phone app itself later
       reads from.
    This one is worth pausing on: the thermostat is initiating the
    action (sending its reading somewhere), which makes IT the client
    in this specific exchange — even though your first instinct might
    be to think of the "app" as always being the client. The role
    isn't fixed to a type of device; it's fixed to who is asking vs
    who is holding/receiving the data in a given exchange. The same
    thermostat could also act as a SERVER in a different exchange —
    for example, if the phone app asks the thermostat directly for
    its current setting.

WHY THIS WORKS AS AN ANSWER
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The client/server distinction isn't about what KIND of device or app
something is — it's about direction: whichever side is INITIATING
the request is the client, and whichever side is HOLDING the data or
doing the work being asked for is the server, for that specific
exchange. Example (c) is the trickiest because it flips the pattern
you'd expect from (a) and (b), which is exactly why it's included —
the same device can be a client in one exchange and a server in
another, depending on which way the request is flowing.