Use “blackboard” in a sentence | “blackboard” sentence examples. 1) The teacher wrote on the blackboard with a piece of chalk. 2) The teacher told us to look at the blackboard. 3) The man standing before the blackboard is our teacher of physics.
“For” has multiple uses; it can function as a coordinating conjunction (one of the F.A.N.B.O.Y.S.) to connect words or groups of words together, but it can also function as a preposition.
ON Use on when something is touching the surface of something. It could be a horizontal surface, like a floor or beach, or a vertical surface, like a wall (“They hung pictures ON the wall”). We also use “on” for the surfaces of body parts (“He has a tattoo ON his arm”).
Prepositions and Time English speakers use in to refer to a general, longer period of time, such as months, years, decades, or centuries. For example, we say “in April,” “in 2015” or “in the 21st century.” Moving to shorter, more specific periods of time, we use on to talk about particular days, dates, and holidays .Feb 15, 2018