What challenges do you face when planning ahead?

During an experiment measuring the change in temperature of a chemical reaction your digital thermometer breaks. you have the same model thermometer available to use how do you proceed with the experiment a. continue on with the new thermometer b. begin the experiment again with the new thermometer c. calibrate the new thermometer and make a notation regarding the change in equipment d. calibrate the new thermometer and begin the experiment again

What is the italicized part in the sentence , all of the operators are efficient.

Ineed . in the first paragraph, the word rival means: a. neighbor b. competitor c. customer d. manufacturer