The key idea is to identify the largest value among a set of numbers. Compare the given times: 15 minutes, 20 minutes, 30 minutes, and 10 minutes. 30 minutes is greater than all the others, so the activity with 30 minutes is the one that has the largest time allocation. The other options are shorter (15, 20, and 10 minutes), so they don’t match the largest allocation.

In the Arrhenius view, the rate constant is k = A exp(-Ea/RT). A catalyst provides an alternative pathway with a lower activation energy Ea. Because the exponent becomes less negative when Ea is smaller, the exponential factor increases, so the rate constant k is larger at any given temperature. Regarding temperature dependence, the slope of a plot of ln k versus 1/T is -Ea/R. Lowering Ea reduces the magnitude of this slope, meaning k becomes less sensitive to temperature changes. So the catalyst not only increases k by lowering Ea, but also makes the temperature dependence weaker. While some catalysts can affect the pre-exponential factor A, the typical and most direct description is that Ea is lowered, leading to a higher k and diminished temperature sensitivity.

A buffer works by using a conjugate acid–base pair to neutralize added acid or base. When a small amount of strong acid is added, the conjugate base (A−) in the buffer reacts with the extra H+ to form the weak acid (HA): A− + H+ → HA. This removes some of the added protons, so the pH rises only a little. When a small amount of strong base is added, the weak acid (HA) donates a proton to the hydroxide: OH− + HA → H2O + A−, forming more of the conjugate base and again limiting the pH change. The Henderson–Hasselbalch expression pH = pKa + log([A−]/[HA]) shows why the pH stays near the pKa: small additions shift the ratio [A−]/[HA] only slightly, keeping pH in a narrow range around the pKa (the buffer range). A few caveats: buffers have finite capacity, so large additions can overwhelm them and cause bigger pH changes; and buffers don’t fix pH absolutely or provide resistance in one direction only.

To solve this, identify every task that is not writing and add up the time for each of those tasks. The question asks for the total time spent on non-writing activities, so you include all non-writing items and exclude any writing tasks. The final sum represents the combined duration of all non-writing tasks. In this problem, the durations of those non-writing tasks add up to 45 minutes, so 45 minutes is the correct total. If you arrive at a different number, it would mean either some non-writing tasks were left out or a writing task was counted by mistake.