By interchanging which two signs the equation will be correct?
$$9 - 11 + 26 \div 78 \times 27 = 11$$

Option (a) $$-\ and\ \times$$

$$9 \times 11 + 26 \div 78 - 27 = 11$$

The given equation will not be satisfied. Because it will give fractional value. So this will not be the correct answer. 

Option (b) $$\times\ and\ \div$$

$$9-11+26\times78\div27=11$$

The given equation will not be satisfied. Because it will give fractional value. So this will not be the correct answer.

Option (c) $$-\ and\ +$$

$$9+11-\frac{26}{78}\times27=11$$

Option (d) $$+\ and\ \div$$

$$9 - 11 \div 26 + 78 \times 27 = 11$$

The given equation will not be satisfied. Because it will give a fractional value. So this will not be the correct answer.