To determine the redundant expressions in the basic blocks \(B4\) and \(B5\), we need to analyze the control flow graph and identify any common subexpressions that have been previously computed and whose variables have not changed since their computation.

Let's examine each block:

1. Basic Block B2:
   • Expressions: \(a = g \times k\), \(f = d - f\), \(a = c \times 4\)
   • \(g \times k\) is computed here.
2. Basic Block B3:
   • Expressions: \(t = g \times k\), \(b = c + m\)
   • \(g \times k\) is recomputed, indicating a potential redundancy if \(g\) or \(k\) have not changed since the last computation.
3. Basic Block B4:
   • Expressions: \(x = g \times k\), \(y = b + i\)
   • \(g \times k\) is a redundant expression because it was already computed in \(B2\) and neither \(g\) nor \(k\) have been altered.
   • \(b + i\) is computed again here, but there's no evidence that it was computed prior to \(B1\) suggesting it is not redundant.
4. Basic Block B5:
   • Expression: \(z = c + m\)
   • \(c + m\) was calculated in \(B3\) but not carried forward to \(B5\) as these blocks do not share a direct relation without a merging point.

Based on this analysis, the redundant expressions in \(B4\) are \(\{g \times k\}\) and there are no redundant expressions in \(B5\).

Correct Answer: B4: \(\{g \times k\}\), B5: \(\{\}\)