s is a subset within a universal set, u. if s = {x, y, 4, 9,?}, which could describe u? u = {keys on a…

s is a subset within a universal set, u. if s = {x, y, 4, 9,?}, which could describe u? u = {keys on a keyboard} u = {letters} u = {numbers} u = {punctuation marks}

s is a subset within a universal set, u. if s = {x, y, 4, 9,?}, which could describe u? u = {keys on a keyboard} u = {letters} u = {numbers} u = {punctuation marks}

Answer

Brief Explanations:

To determine the universal set ( U ) that can contain the subset ( S={x, y, 4, 9,?} ), we analyze each option:

  • Option "U = {letters}": The set ( S ) contains numbers (4, 9) and a punctuation mark (?), so it can't be a subset of just letters.
  • Option "U = {numbers}": The set ( S ) contains letters (x, y) and a punctuation mark (?), so it can't be a subset of just numbers.
  • Option "U = {punctuation marks}": The set ( S ) contains letters (x, y) and numbers (4, 9), so it can't be a subset of just punctuation marks.
  • Option "U = {keys on a keyboard}": A keyboard has letter keys (x, y), number keys (4, 9), and punctuation keys (?), so ( S ) can be a subset of the set of keyboard keys.

Answer:

A. ( U = {\text{keys on a keyboard}} )