The directions for an experiment being carried out to determine the molar mass of a monoprotic organic acid are as follows.
"Place 0.5 g (± 0.1 mg) of the unknown solid acid in a 125-mL Erlenmeyer flask. Add approximately 30 mL of distilled water and two drops of bromothymol blue indicator. Titrate the resulting solution to the bromothymol blue endpoint."
Of the four choices listed below (not including ordinary glassware), which of the following includes ONLY those items of equipment needed to carry out this step?