Question

grammar passage
bacteria in hailstones
airborne bacteria have lately 23 generated a lot of interest, due to 24 its ubiquitous presence and the accumulating evidence of their activity in the atmosphere. previous studies 25 indicate that soils and plant leaf surfaces are major sources of airborne bacteria, whereas marine environments are a less prominent source.
(1) 26 diverse bacterial communities have been described in the atmosphere and in
clouds. (2) 27 similarly, bacterial communities in cloud water may be distinct from bacterial communities in the dry atmosphere, as the chances of airborne bacteria to enter into cloud droplets are increased for those that can act as cloud condensation nuclei. (3) after entering cloud droplets,
28 they are thought to influence physical and chemical processes in the atmosphere. (4) 29 during their time in
clouds, gram - negative bacteria (bacteria with a different cell wall which is indicated by the gram stain when tested in laboratories) could influence patterns of precipitation by facilitating the formation of ice crystals. (5) the so - called ice nucleation active (ina) bacteria are among the most efficient described ice nucleators. (6) by forming large aggregates of ina proteins, which are anchored in their outer membrane,
ina bacteria 30 raise by a lot the freezing temperature
of water.
inside storm clouds, water droplets can coalesce into
hint: most act english questions can be answered by looking at the referenced sentence without reading the whole passage
question 5 / 5
this question refers to 25
choose the option that best improves underlined portion number 25.
a no change
b indicate: that
c indicate, that
d indicate that

Explanation:

To solve this, we analyze the context and grammar. The sentence "Previous studies 25 indicate that..." has a subject "Previous studies" (plural) and the verb "indicate" should be in present tense (since the studies' findings are a general statement). The original "indicate—that" has an incorrect em - dash; the correct structure is "indicate that" (no colon or comma, just the conjunction "that" to introduce the clause). Option A has an incorrect em - dash, B has a colon (unnecessary), C has a comma (incorrect for introducing the clause). Option D uses "indicate that" which is grammatically correct.

Answer:

D. indicate that