Chữ số thích hợp viết vào ô trống là

A. 6

B. 7

C. 8

D. 9

Read the following passage and choose the best answer for each blank.

Attractive landscape sites, such as sandy beaches, lakes, riversides, and mountain tops and slopes, are often affected by mass tourism. Physical (26) _______ are caused not only by clearing and construction of tourism-related land, but by continuing tourist activities and (27) _______changes in local economies and ecologies.

The development of tourism (28) _______such as accommodation, water supplies, can (29) _______ sand mining, beach and sand dune erosion, soil erosion and extensive paving. In addition, road and airport construction can lead to land degradation and loss of wildlife habitats and deterioration of scenery.

In Yosemite National Park in the United States, for instance, the number of roads and facilities (30) _______ to keep pace with the growing visitor numbers and to supply facilities, infrastructure and parking lots for all these tourists. These actions have caused (31) _______loss in the park and are (32) _______by various forms of pollution including air pollution from automobile emissions. The authorities have reported, "Smog was (33)_______that Yosemite Valley could not be seen from airplanes". This occasional smog is harmful to all species and vegetation inside the park.

Construction of ski resort accommodation and facilities frequently (34) _______clearing forested land. Coastal wetlands are often drained and filled due to lack of more suitable sites for construction of tourism facilities and infrastructure. These activities can cause severe disturbance and erosion of the local (35) _______, even destruction in the long term.

The development of tourism (28) _______such as accommodation,

A. features

B. activities

C. abilities

D. facilities

A. frontiersman

B. most

C. of

D. hero

Một cá thể có kiểu gen Dd A b a b  tạo ra giao tử  D ab với tỉ lệ:

A. 12,5%

B. 50%

C. 25%

D. 20%