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 about 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?