\textbf{Use Punnett squares to answer questions 8, 9 and 10. In guinea pigs, coat texture is determined by a complete dominance gene: rough coats are dominant to smooth coats.}  Two guinea pigs heterozygous for coat texture have offspring. What is the percent of their offspring expected to have smooth coats? 
选项为:A:0\%  B:25\%  C:50\%  D:75\%  E:100\%  请回答其中一个选项.