Which one of the following figures correctly shows the dotted line at the point of critical radius/ maximum heat transfer rate for a cylindrical tube wall?

• A. <a href="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12a.png"><img alt="Line at point of critical radius heat transfer rate for cylindrical tube wall - option a" class="alignnone size-full wp-image-246515" height="394" sizes="(max-width: 567px) 100vw, 567px" src="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12a.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12a.png 567w, https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12a-300x208.png 300w" width="567"/></a>
• B. <a href="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12b.png"><img alt="Line at point of critical radius heat transfer rate for cylindrical tube wall - option b" class="alignnone size-full wp-image-246516" height="403" sizes="(max-width: 565px) 100vw, 565px" src="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12b.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12b.png 565w, https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12b-300x214.png 300w" width="565"/></a>
• C. <a href="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12c.png"><img alt="Line at point of critical radius heat transfer rate for cylindrical tube wall - option c" class="alignnone size-full wp-image-246517" height="407" sizes="(max-width: 571px) 100vw, 571px" src="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12c.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12c.png 571w, https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12c-300x214.png 300w" width="571"/></a>
• D. <a href="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12d.png"><img alt="Line at point of critical radius heat transfer rate for cylindrical tube wall - option d" class="alignnone size-full wp-image-246518" height="402" sizes="(max-width: 570px) 100vw, 570px" src="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12d.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12d.png 570w, https://www.sanfoundry.com/wp-content/uploads/2019/09/heat-transfer-operations-questions-answers-combined-heat-transfer-conduction-convection-q12d-300x212.png 300w" width="570"/></a>