challenge: What is the primary method by which 2,4,6-tri-tert-butylphenol was first described to be prepared?
  
  A. Base-catalyzed reaction of phenol with isobutylene
  B. Photochemical reaction of phenol with isobutylene
  C. Acid-catalyzed reaction of phenol with isobutylene
  D. Heat-induced reaction of phenol with isobutylene
  Answer: 